/*
 * apply.c
 *
 * Copyright (C) Linus Torvalds, 2005
 *
 * This applies patches on top of some (arbitrary) version of the SCM.
 *
 */
#include "cache.h"
#include "cache-tree.h"
#include "quote.h"
#include "blob.h"
#include "delta.h"
#include "builtin.h"
#include "string-list.h"
#include "dir.h"
#include "diff.h"
#include "parse-options.h"
#include "xdiff-interface.h"
#include "ll-merge.h"
#include "rerere.h"

/*
 *  --check turns on checking that the working tree matches the
 *    files that are being modified, but doesn't apply the patch
 *  --stat does just a diffstat, and doesn't actually apply
 *  --numstat does numeric diffstat, and doesn't actually apply
 *  --index-info shows the old and new index info for paths if available.
 *  --index updates the cache as well.
 *  --cached updates only the cache without ever touching the working tree.
 */
static const char *prefix;
static int prefix_length = -1;
static int newfd = -1;

static int unidiff_zero;
static int p_value = 1;
static int p_value_known;
static int check_index;
static int update_index;
static int cached;
static int diffstat;
static int numstat;
static int summary;
static int check;
static int apply = 1;
static int apply_in_reverse;
static int apply_with_reject;
static int apply_verbosely;
static int allow_overlap;
static int no_add;
static int threeway;
static const char *fake_ancestor;
static int line_termination = '\n';
static unsigned int p_context = UINT_MAX;
static const char * const apply_usage[] = {
        N_("git apply [options] [<patch>...]"),
        NULL
};

static enum ws_error_action {
        nowarn_ws_error,
        warn_on_ws_error,
        die_on_ws_error,
        correct_ws_error
} ws_error_action = warn_on_ws_error;
static int whitespace_error;
static int squelch_whitespace_errors = 5;
static int applied_after_fixing_ws;

static enum ws_ignore {
        ignore_ws_none,
        ignore_ws_change
} ws_ignore_action = ignore_ws_none;


static const char *patch_input_file;
static const char *root;
static int root_len;
static int read_stdin = 1;
static int options;

static void parse_whitespace_option(const char *option)
{
        if (!option) {
                ws_error_action = warn_on_ws_error;
                return;
        }
        if (!strcmp(option, "warn")) {
                ws_error_action = warn_on_ws_error;
                return;
        }
        if (!strcmp(option, "nowarn")) {
                ws_error_action = nowarn_ws_error;
                return;
        }
        if (!strcmp(option, "error")) {
                ws_error_action = die_on_ws_error;
                return;
        }
        if (!strcmp(option, "error-all")) {
                ws_error_action = die_on_ws_error;
                squelch_whitespace_errors = 0;
                return;
        }
        if (!strcmp(option, "strip") || !strcmp(option, "fix")) {
                ws_error_action = correct_ws_error;
                return;
        }
        die(_("unrecognized whitespace option '%s'"), option);
}

static void parse_ignorewhitespace_option(const char *option)
{
        if (!option || !strcmp(option, "no") ||
            !strcmp(option, "false") || !strcmp(option, "never") ||
            !strcmp(option, "none")) {
                ws_ignore_action = ignore_ws_none;
                return;
        }
        if (!strcmp(option, "change")) {
                ws_ignore_action = ignore_ws_change;
                return;
        }
        die(_("unrecognized whitespace ignore option '%s'"), option);
}

static void set_default_whitespace_mode(const char *whitespace_option)
{
        if (!whitespace_option && !apply_default_whitespace)
                ws_error_action = (apply ? warn_on_ws_error : nowarn_ws_error);
}

/*
 * For "diff-stat" like behaviour, we keep track of the biggest change
 * we've seen, and the longest filename. That allows us to do simple
 * scaling.
 */
static int max_change, max_len;

/*
 * Various "current state", notably line numbers and what
 * file (and how) we're patching right now.. The "is_xxxx"
 * things are flags, where -1 means "don't know yet".
 */
static int linenr = 1;

/*
 * This represents one "hunk" from a patch, starting with
 * "@@ -oldpos,oldlines +newpos,newlines @@" marker.  The
 * patch text is pointed at by patch, and its byte length
 * is stored in size.  leading and trailing are the number
 * of context lines.
 */
struct fragment {
        unsigned long leading, trailing;
        unsigned long oldpos, oldlines;
        unsigned long newpos, newlines;
        /*
         * 'patch' is usually borrowed from buf in apply_patch(),
         * but some codepaths store an allocated buffer.
         */
        const char *patch;
        unsigned free_patch:1,
                rejected:1;
        int size;
        int linenr;
        struct fragment *next;
};

/*
 * When dealing with a binary patch, we reuse "leading" field
 * to store the type of the binary hunk, either deflated "delta"
 * or deflated "literal".
 */
#define binary_patch_method leading
#define BINARY_DELTA_DEFLATED   1
#define BINARY_LITERAL_DEFLATED 2

/*
 * This represents a "patch" to a file, both metainfo changes
 * such as creation/deletion, filemode and content changes represented
 * as a series of fragments.
 */
struct patch {
        char *new_name, *old_name, *def_name;
        unsigned int old_mode, new_mode;
        int is_new, is_delete;  /* -1 = unknown, 0 = false, 1 = true */
        int rejected;
        unsigned ws_rule;
        int lines_added, lines_deleted;
        int score;
        unsigned int is_toplevel_relative:1;
        unsigned int inaccurate_eof:1;
        unsigned int is_binary:1;
        unsigned int is_copy:1;
        unsigned int is_rename:1;
        unsigned int recount:1;
        unsigned int conflicted_threeway:1;
        unsigned int direct_to_threeway:1;
        struct fragment *fragments;
        char *result;
        size_t resultsize;
        char old_sha1_prefix[41];
        char new_sha1_prefix[41];
        struct patch *next;

        /* three-way fallback result */
        unsigned char threeway_stage[3][20];
};

static void free_fragment_list(struct fragment *list)
{
        while (list) {
                struct fragment *next = list->next;
                if (list->free_patch)
                        free((char *)list->patch);
                free(list);
                list = next;
        }
}

static void free_patch(struct patch *patch)
{
        free_fragment_list(patch->fragments);
        free(patch->def_name);
        free(patch->old_name);
        free(patch->new_name);
        free(patch->result);
        free(patch);
}

static void free_patch_list(struct patch *list)
{
        while (list) {
                struct patch *next = list->next;
                free_patch(list);
                list = next;
        }
}

/*
 * A line in a file, len-bytes long (includes the terminating LF,
 * except for an incomplete line at the end if the file ends with
 * one), and its contents hashes to 'hash'.
 */
struct line {
        size_t len;
        unsigned hash : 24;
        unsigned flag : 8;
#define LINE_COMMON     1
#define LINE_PATCHED    2
};

/*
 * This represents a "file", which is an array of "lines".
 */
struct image {
        char *buf;
        size_t len;
        size_t nr;
        size_t alloc;
        struct line *line_allocated;
        struct line *line;
};

/*
 * Records filenames that have been touched, in order to handle
 * the case where more than one patches touch the same file.
 */

static struct string_list fn_table;

static uint32_t hash_line(const char *cp, size_t len)
{
        size_t i;
        uint32_t h;
        for (i = 0, h = 0; i < len; i++) {
                if (!isspace(cp[i])) {
                        h = h * 3 + (cp[i] & 0xff);
                }
        }
        return h;
}

/*
 * Compare lines s1 of length n1 and s2 of length n2, ignoring
 * whitespace difference. Returns 1 if they match, 0 otherwise
 */
static int fuzzy_matchlines(const char *s1, size_t n1,
                            const char *s2, size_t n2)
{
        const char *last1 = s1 + n1 - 1;
        const char *last2 = s2 + n2 - 1;
        int result = 0;

        /* ignore line endings */
        while ((*last1 == '\r') || (*last1 == '\n'))
                last1--;
        while ((*last2 == '\r') || (*last2 == '\n'))
                last2--;

        /* skip leading whitespaces, if both begin with whitespace */
        if (s1 <= last1 && s2 <= last2 && isspace(*s1) && isspace(*s2)) {
                while (isspace(*s1) && (s1 <= last1))
                        s1++;
                while (isspace(*s2) && (s2 <= last2))
                        s2++;
        }
        /* early return if both lines are empty */
        if ((s1 > last1) && (s2 > last2))
                return 1;
        while (!result) {
                result = *s1++ - *s2++;
                /*
                 * Skip whitespace inside. We check for whitespace on
                 * both buffers because we don't want "a b" to match
                 * "ab"
                 */
                if (isspace(*s1) && isspace(*s2)) {
                        while (isspace(*s1) && s1 <= last1)
                                s1++;
                        while (isspace(*s2) && s2 <= last2)
                                s2++;
                }
                /*
                 * If we reached the end on one side only,
                 * lines don't match
                 */
                if (
                    ((s2 > last2) && (s1 <= last1)) ||
                    ((s1 > last1) && (s2 <= last2)))
                        return 0;
                if ((s1 > last1) && (s2 > last2))
                        break;
        }

        return !result;
}

static void add_line_info(struct image *img, const char *bol, size_t len, unsigned flag)
{
        ALLOC_GROW(img->line_allocated, img->nr + 1, img->alloc);
        img->line_allocated[img->nr].len = len;
        img->line_allocated[img->nr].hash = hash_line(bol, len);
        img->line_allocated[img->nr].flag = flag;
        img->nr++;
}

/*
 * "buf" has the file contents to be patched (read from various sources).
 * attach it to "image" and add line-based index to it.
 * "image" now owns the "buf".
 */
static void prepare_image(struct image *image, char *buf, size_t len,
                          int prepare_linetable)
{
        const char *cp, *ep;

        memset(image, 0, sizeof(*image));
        image->buf = buf;
        image->len = len;

        if (!prepare_linetable)
                return;

        ep = image->buf + image->len;
        cp = image->buf;
        while (cp < ep) {
                const char *next;
                for (next = cp; next < ep && *next != '\n'; next++)
                        ;
                if (next < ep)
                        next++;
                add_line_info(image, cp, next - cp, 0);
                cp = next;
        }
        image->line = image->line_allocated;
}

static void clear_image(struct image *image)
{
        free(image->buf);
        free(image->line_allocated);
        memset(image, 0, sizeof(*image));
}

/* fmt must contain _one_ %s and no other substitution */
static void say_patch_name(FILE *output, const char *fmt, struct patch *patch)
{
        struct strbuf sb = STRBUF_INIT;

        if (patch->old_name && patch->new_name &&
            strcmp(patch->old_name, patch->new_name)) {
                quote_c_style(patch->old_name, &sb, NULL, 0);
                strbuf_addstr(&sb, " => ");
                quote_c_style(patch->new_name, &sb, NULL, 0);
        } else {
                const char *n = patch->new_name;
                if (!n)
                        n = patch->old_name;
                quote_c_style(n, &sb, NULL, 0);
        }
        fprintf(output, fmt, sb.buf);
        fputc('\n', output);
        strbuf_release(&sb);
}

#define SLOP (16)

static void read_patch_file(struct strbuf *sb, int fd)
{
        if (strbuf_read(sb, fd, 0) < 0)
                die_errno("git apply: failed to read");

        /*
         * Make sure that we have some slop in the buffer
         * so that we can do speculative "memcmp" etc, and
         * see to it that it is NUL-filled.
         */
        strbuf_grow(sb, SLOP);
        memset(sb->buf + sb->len, 0, SLOP);
}

static unsigned long linelen(const char *buffer, unsigned long size)
{
        unsigned long len = 0;
        while (size--) {
                len++;
                if (*buffer++ == '\n')
                        break;
        }
        return len;
}

static int is_dev_null(const char *str)
{
        return !memcmp("/dev/null", str, 9) && isspace(str[9]);
}

#define TERM_SPACE      1
#define TERM_TAB        2

static int name_terminate(const char *name, int namelen, int c, int terminate)
{
        if (c == ' ' && !(terminate & TERM_SPACE))
                return 0;
        if (c == '\t' && !(terminate & TERM_TAB))
                return 0;

        return 1;
}

/* remove double slashes to make --index work with such filenames */
static char *squash_slash(char *name)
{
        int i = 0, j = 0;

        if (!name)
                return NULL;

        while (name[i]) {
                if ((name[j++] = name[i++]) == '/')
                        while (name[i] == '/')
                                i++;
        }
        name[j] = '\0';
        return name;
}

static char *find_name_gnu(const char *line, const char *def, int p_value)
{
        struct strbuf name = STRBUF_INIT;
        char *cp;

        /*
         * Proposed "new-style" GNU patch/diff format; see
         * http://marc.info/?l=git&m=112927316408690&w=2
         */
        if (unquote_c_style(&name, line, NULL)) {
                strbuf_release(&name);
                return NULL;
        }

        for (cp = name.buf; p_value; p_value--) {
                cp = strchr(cp, '/');
                if (!cp) {
                        strbuf_release(&name);
                        return NULL;
                }
                cp++;
        }

        strbuf_remove(&name, 0, cp - name.buf);
        if (root)
                strbuf_insert(&name, 0, root, root_len);
        return squash_slash(strbuf_detach(&name, NULL));
}

static size_t sane_tz_len(const char *line, size_t len)
{
        const char *tz, *p;

        if (len < strlen(" +0500") || line[len-strlen(" +0500")] != ' ')
                return 0;
        tz = line + len - strlen(" +0500");

        if (tz[1] != '+' && tz[1] != '-')
                return 0;

        for (p = tz + 2; p != line + len; p++)
                if (!isdigit(*p))
                        return 0;

        return line + len - tz;
}

static size_t tz_with_colon_len(const char *line, size_t len)
{
        const char *tz, *p;

        if (len < strlen(" +08:00") || line[len - strlen(":00")] != ':')
                return 0;
        tz = line + len - strlen(" +08:00");

        if (tz[0] != ' ' || (tz[1] != '+' && tz[1] != '-'))
                return 0;
        p = tz + 2;
        if (!isdigit(*p++) || !isdigit(*p++) || *p++ != ':' ||
            !isdigit(*p++) || !isdigit(*p++))
                return 0;

        return line + len - tz;
}

static size_t date_len(const char *line, size_t len)
{
        const char *date, *p;

        if (len < strlen("72-02-05") || line[len-strlen("-05")] != '-')
                return 0;
        p = date = line + len - strlen("72-02-05");

        if (!isdigit(*p++) || !isdigit(*p++) || *p++ != '-' ||
            !isdigit(*p++) || !isdigit(*p++) || *p++ != '-' ||
            !isdigit(*p++) || !isdigit(*p++))   /* Not a date. */
                return 0;

        if (date - line >= strlen("19") &&
            isdigit(date[-1]) && isdigit(date[-2]))     /* 4-digit year */
                date -= strlen("19");

        return line + len - date;
}

static size_t short_time_len(const char *line, size_t len)
{
        const char *time, *p;

        if (len < strlen(" 07:01:32") || line[len-strlen(":32")] != ':')
                return 0;
        p = time = line + len - strlen(" 07:01:32");

        /* Permit 1-digit hours? */
        if (*p++ != ' ' ||
            !isdigit(*p++) || !isdigit(*p++) || *p++ != ':' ||
            !isdigit(*p++) || !isdigit(*p++) || *p++ != ':' ||
            !isdigit(*p++) || !isdigit(*p++))   /* Not a time. */
                return 0;

        return line + len - time;
}

static size_t fractional_time_len(const char *line, size_t len)
{
        const char *p;
        size_t n;

        /* Expected format: 19:41:17.620000023 */
        if (!len || !isdigit(line[len - 1]))
                return 0;
        p = line + len - 1;

        /* Fractional seconds. */
        while (p > line && isdigit(*p))
                p--;
        if (*p != '.')
                return 0;

        /* Hours, minutes, and whole seconds. */
        n = short_time_len(line, p - line);
        if (!n)
                return 0;

        return line + len - p + n;
}

static size_t trailing_spaces_len(const char *line, size_t len)
{
        const char *p;

        /* Expected format: ' ' x (1 or more)  */
        if (!len || line[len - 1] != ' ')
                return 0;

        p = line + len;
        while (p != line) {
                p--;
                if (*p != ' ')
                        return line + len - (p + 1);
        }

        /* All spaces! */
        return len;
}

static size_t diff_timestamp_len(const char *line, size_t len)
{
        const char *end = line + len;
        size_t n;

        /*
         * Posix: 2010-07-05 19:41:17
         * GNU: 2010-07-05 19:41:17.620000023 -0500
         */

        if (!isdigit(end[-1]))
                return 0;

        n = sane_tz_len(line, end - line);
        if (!n)
                n = tz_with_colon_len(line, end - line);
        end -= n;

        n = short_time_len(line, end - line);
        if (!n)
                n = fractional_time_len(line, end - line);
        end -= n;

        n = date_len(line, end - line);
        if (!n) /* No date.  Too bad. */
                return 0;
        end -= n;

        if (end == line)        /* No space before date. */
                return 0;
        if (end[-1] == '\t') {  /* Success! */
                end--;
                return line + len - end;
        }
        if (end[-1] != ' ')     /* No space before date. */
                return 0;

        /* Whitespace damage. */
        end -= trailing_spaces_len(line, end - line);
        return line + len - end;
}

static char *null_strdup(const char *s)
{
        return s ? xstrdup(s) : NULL;
}

static char *find_name_common(const char *line, const char *def,
                              int p_value, const char *end, int terminate)
{
        int len;
        const char *start = NULL;

        if (p_value == 0)
                start = line;
        while (line != end) {
                char c = *line;

                if (!end && isspace(c)) {
                        if (c == '\n')
                                break;
                        if (name_terminate(start, line-start, c, terminate))
                                break;
                }
                line++;
                if (c == '/' && !--p_value)
                        start = line;
        }
        if (!start)
                return squash_slash(null_strdup(def));
        len = line - start;
        if (!len)
                return squash_slash(null_strdup(def));

        /*
         * Generally we prefer the shorter name, especially
         * if the other one is just a variation of that with
         * something else tacked on to the end (ie "file.orig"
         * or "file~").
         */
        if (def) {
                int deflen = strlen(def);
                if (deflen < len && !strncmp(start, def, deflen))
                        return squash_slash(xstrdup(def));
        }

        if (root) {
                char *ret = xmalloc(root_len + len + 1);
                strcpy(ret, root);
                memcpy(ret + root_len, start, len);
                ret[root_len + len] = '\0';
                return squash_slash(ret);
        }

        return squash_slash(xmemdupz(start, len));
}

static char *find_name(const char *line, char *def, int p_value, int terminate)
{
        if (*line == '"') {
                char *name = find_name_gnu(line, def, p_value);
                if (name)
                        return name;
        }

        return find_name_common(line, def, p_value, NULL, terminate);
}

static char *find_name_traditional(const char *line, char *def, int p_value)
{
        size_t len;
        size_t date_len;

        if (*line == '"') {
                char *name = find_name_gnu(line, def, p_value);
                if (name)
                        return name;
        }

        len = strchrnul(line, '\n') - line;
        date_len = diff_timestamp_len(line, len);
        if (!date_len)
                return find_name_common(line, def, p_value, NULL, TERM_TAB);
        len -= date_len;

        return find_name_common(line, def, p_value, line + len, 0);
}

static int count_slashes(const char *cp)
{
        int cnt = 0;
        char ch;

        while ((ch = *cp++))
                if (ch == '/')
                        cnt++;
        return cnt;
}

/*
 * Given the string after "--- " or "+++ ", guess the appropriate
 * p_value for the given patch.
 */
static int guess_p_value(const char *nameline)
{
        char *name, *cp;
        int val = -1;

        if (is_dev_null(nameline))
                return -1;
        name = find_name_traditional(nameline, NULL, 0);
        if (!name)
                return -1;
        cp = strchr(name, '/');
        if (!cp)
                val = 0;
        else if (prefix) {
                /*
                 * Does it begin with "a/$our-prefix" and such?  Then this is
                 * very likely to apply to our directory.
                 */
                if (!strncmp(name, prefix, prefix_length))
                        val = count_slashes(prefix);
                else {
                        cp++;
                        if (!strncmp(cp, prefix, prefix_length))
                                val = count_slashes(prefix) + 1;
                }
        }
        free(name);
        return val;
}

/*
 * Does the ---/+++ line has the POSIX timestamp after the last HT?
 * GNU diff puts epoch there to signal a creation/deletion event.  Is
 * this such a timestamp?
 */
static int has_epoch_timestamp(const char *nameline)
{
        /*
         * We are only interested in epoch timestamp; any non-zero
         * fraction cannot be one, hence "(\.0+)?" in the regexp below.
         * For the same reason, the date must be either 1969-12-31 or
         * 1970-01-01, and the seconds part must be "00".
         */
        const char stamp_regexp[] =
                "^(1969-12-31|1970-01-01)"
                " "
                "[0-2][0-9]:[0-5][0-9]:00(\\.0+)?"
                " "
                "([-+][0-2][0-9]:?[0-5][0-9])\n";
        const char *timestamp = NULL, *cp, *colon;
        static regex_t *stamp;
        regmatch_t m[10];
        int zoneoffset;
        int hourminute;
        int status;

        for (cp = nameline; *cp != '\n'; cp++) {
                if (*cp == '\t')
                        timestamp = cp + 1;
        }
        if (!timestamp)
                return 0;
        if (!stamp) {
                stamp = xmalloc(sizeof(*stamp));
                if (regcomp(stamp, stamp_regexp, REG_EXTENDED)) {
                        warning(_("Cannot prepare timestamp regexp %s"),
                                stamp_regexp);
                        return 0;
                }
        }

        status = regexec(stamp, timestamp, ARRAY_SIZE(m), m, 0);
        if (status) {
                if (status != REG_NOMATCH)
                        warning(_("regexec returned %d for input: %s"),
                                status, timestamp);
                return 0;
        }

        zoneoffset = strtol(timestamp + m[3].rm_so + 1, (char **) &colon, 10);
        if (*colon == ':')
                zoneoffset = zoneoffset * 60 + strtol(colon + 1, NULL, 10);
        else
                zoneoffset = (zoneoffset / 100) * 60 + (zoneoffset % 100);
        if (timestamp[m[3].rm_so] == '-')
                zoneoffset = -zoneoffset;

        /*
         * YYYY-MM-DD hh:mm:ss must be from either 1969-12-31
         * (west of GMT) or 1970-01-01 (east of GMT)
         */
        if ((zoneoffset < 0 && memcmp(timestamp, "1969-12-31", 10)) ||
            (0 <= zoneoffset && memcmp(timestamp, "1970-01-01", 10)))
                return 0;

        hourminute = (strtol(timestamp + 11, NULL, 10) * 60 +
                      strtol(timestamp + 14, NULL, 10) -
                      zoneoffset);

        return ((zoneoffset < 0 && hourminute == 1440) ||
                (0 <= zoneoffset && !hourminute));
}

/*
 * Get the name etc info from the ---/+++ lines of a traditional patch header
 *
 * FIXME! The end-of-filename heuristics are kind of screwy. For existing
 * files, we can happily check the index for a match, but for creating a
 * new file we should try to match whatever "patch" does. I have no idea.
 */
static void parse_traditional_patch(const char *first, const char *second, struct patch *patch)
{
        char *name;

        first += 4;     /* skip "--- " */
        second += 4;    /* skip "+++ " */
        if (!p_value_known) {
                int p, q;
                p = guess_p_value(first);
                q = guess_p_value(second);
                if (p < 0) p = q;
                if (0 <= p && p == q) {
                        p_value = p;
                        p_value_known = 1;
                }
        }
        if (is_dev_null(first)) {
                patch->is_new = 1;
                patch->is_delete = 0;
                name = find_name_traditional(second, NULL, p_value);
                patch->new_name = name;
        } else if (is_dev_null(second)) {
                patch->is_new = 0;
                patch->is_delete = 1;
                name = find_name_traditional(first, NULL, p_value);
                patch->old_name = name;
        } else {
                char *first_name;
                first_name = find_name_traditional(first, NULL, p_value);
                name = find_name_traditional(second, first_name, p_value);
                free(first_name);
                if (has_epoch_timestamp(first)) {
                        patch->is_new = 1;
                        patch->is_delete = 0;
                        patch->new_name = name;
                } else if (has_epoch_timestamp(second)) {
                        patch->is_new = 0;
                        patch->is_delete = 1;
                        patch->old_name = name;
                } else {
                        patch->old_name = name;
                        patch->new_name = null_strdup(name);
                }
        }
        if (!name)
                die(_("unable to find filename in patch at line %d"), linenr);
}

static int gitdiff_hdrend(const char *line, struct patch *patch)
{
        return -1;
}

/*
 * We're anal about diff header consistency, to make
 * sure that we don't end up having strange ambiguous
 * patches floating around.
 *
 * As a result, gitdiff_{old|new}name() will check
 * their names against any previous information, just
 * to make sure..
 */
#define DIFF_OLD_NAME 0
#define DIFF_NEW_NAME 1

static char *gitdiff_verify_name(const char *line, int isnull, char *orig_name, int side)
{
        if (!orig_name && !isnull)
                return find_name(line, NULL, p_value, TERM_TAB);

        if (orig_name) {
                int len;
                const char *name;
                char *another;
                name = orig_name;
                len = strlen(name);
                if (isnull)
                        die(_("git apply: bad git-diff - expected /dev/null, got %s on line %d"), name, linenr);
                another = find_name(line, NULL, p_value, TERM_TAB);
                if (!another || memcmp(another, name, len + 1))
                        die((side == DIFF_NEW_NAME) ?
                            _("git apply: bad git-diff - inconsistent new filename on line %d") :
                            _("git apply: bad git-diff - inconsistent old filename on line %d"), linenr);
                free(another);
                return orig_name;
        }
        else {
                /* expect "/dev/null" */
                if (memcmp("/dev/null", line, 9) || line[9] != '\n')
                        die(_("git apply: bad git-diff - expected /dev/null on line %d"), linenr);
                return NULL;
        }
}

static int gitdiff_oldname(const char *line, struct patch *patch)
{
        char *orig = patch->old_name;
        patch->old_name = gitdiff_verify_name(line, patch->is_new, patch->old_name,
                                              DIFF_OLD_NAME);
        if (orig != patch->old_name)
                free(orig);
        return 0;
}

static int gitdiff_newname(const char *line, struct patch *patch)
{
        char *orig = patch->new_name;
        patch->new_name = gitdiff_verify_name(line, patch->is_delete, patch->new_name,
                                              DIFF_NEW_NAME);
        if (orig != patch->new_name)
                free(orig);
        return 0;
}

static int gitdiff_oldmode(const char *line, struct patch *patch)
{
        patch->old_mode = strtoul(line, NULL, 8);
        return 0;
}

static int gitdiff_newmode(const char *line, struct patch *patch)
{
        patch->new_mode = strtoul(line, NULL, 8);
        return 0;
}

static int gitdiff_delete(const char *line, struct patch *patch)
{
        patch->is_delete = 1;
        free(patch->old_name);
        patch->old_name = null_strdup(patch->def_name);
        return gitdiff_oldmode(line, patch);
}

static int gitdiff_newfile(const char *line, struct patch *patch)
{
        patch->is_new = 1;
        free(patch->new_name);
        patch->new_name = null_strdup(patch->def_name);
        return gitdiff_newmode(line, patch);
}

static int gitdiff_copysrc(const char *line, struct patch *patch)
{
        patch->is_copy = 1;
        free(patch->old_name);
        patch->old_name = find_name(line, NULL, p_value ? p_value - 1 : 0, 0);
        return 0;
}

static int gitdiff_copydst(const char *line, struct patch *patch)
{
        patch->is_copy = 1;
        free(patch->new_name);
        patch->new_name = find_name(line, NULL, p_value ? p_value - 1 : 0, 0);
        return 0;
}

static int gitdiff_renamesrc(const char *line, struct patch *patch)
{
        patch->is_rename = 1;
        free(patch->old_name);
        patch->old_name = find_name(line, NULL, p_value ? p_value - 1 : 0, 0);
        return 0;
}

static int gitdiff_renamedst(const char *line, struct patch *patch)
{
        patch->is_rename = 1;
        free(patch->new_name);
        patch->new_name = find_name(line, NULL, p_value ? p_value - 1 : 0, 0);
        return 0;
}

static int gitdiff_similarity(const char *line, struct patch *patch)
{
        unsigned long val = strtoul(line, NULL, 10);
        if (val <= 100)
                patch->score = val;
        return 0;
}

static int gitdiff_dissimilarity(const char *line, struct patch *patch)
{
        unsigned long val = strtoul(line, NULL, 10);
        if (val <= 100)
                patch->score = val;
        return 0;
}

static int gitdiff_index(const char *line, struct patch *patch)
{
        /*
         * index line is N hexadecimal, "..", N hexadecimal,
         * and optional space with octal mode.
         */
        const char *ptr, *eol;
        int len;

        ptr = strchr(line, '.');
        if (!ptr || ptr[1] != '.' || 40 < ptr - line)
                return 0;
        len = ptr - line;
        memcpy(patch->old_sha1_prefix, line, len);
        patch->old_sha1_prefix[len] = 0;

        line = ptr + 2;
        ptr = strchr(line, ' ');
        eol = strchrnul(line, '\n');

        if (!ptr || eol < ptr)
                ptr = eol;
        len = ptr - line;

        if (40 < len)
                return 0;
        memcpy(patch->new_sha1_prefix, line, len);
        patch->new_sha1_prefix[len] = 0;
        if (*ptr == ' ')
                patch->old_mode = strtoul(ptr+1, NULL, 8);
        return 0;
}

/*
 * This is normal for a diff that doesn't change anything: we'll fall through
 * into the next diff. Tell the parser to break out.
 */
static int gitdiff_unrecognized(const char *line, struct patch *patch)
{
        return -1;
}

/*
 * Skip p_value leading components from "line"; as we do not accept
 * absolute paths, return NULL in that case.
 */
static const char *skip_tree_prefix(const char *line, int llen)
{
        int nslash;
        int i;

        if (!p_value)
                return (llen && line[0] == '/') ? NULL : line;

        nslash = p_value;
        for (i = 0; i < llen; i++) {
                int ch = line[i];
                if (ch == '/' && --nslash <= 0)
                        return (i == 0) ? NULL : &line[i + 1];
        }
        return NULL;
}

/*
 * This is to extract the same name that appears on "diff --git"
 * line.  We do not find and return anything if it is a rename
 * patch, and it is OK because we will find the name elsewhere.
 * We need to reliably find name only when it is mode-change only,
 * creation or deletion of an empty file.  In any of these cases,
 * both sides are the same name under a/ and b/ respectively.
 */
static char *git_header_name(const char *line, int llen)
{
        const char *name;
        const char *second = NULL;
        size_t len, line_len;

        line += strlen("diff --git ");
        llen -= strlen("diff --git ");

        if (*line == '"') {
                const char *cp;
                struct strbuf first = STRBUF_INIT;
                struct strbuf sp = STRBUF_INIT;

                if (unquote_c_style(&first, line, &second))
                        goto free_and_fail1;

                /* strip the a/b prefix including trailing slash */
                cp = skip_tree_prefix(first.buf, first.len);
                if (!cp)
                        goto free_and_fail1;
                strbuf_remove(&first, 0, cp - first.buf);

                /*
                 * second points at one past closing dq of name.
                 * find the second name.
                 */
                while ((second < line + llen) && isspace(*second))
                        second++;

                if (line + llen <= second)
                        goto free_and_fail1;
                if (*second == '"') {
                        if (unquote_c_style(&sp, second, NULL))
                                goto free_and_fail1;
                        cp = skip_tree_prefix(sp.buf, sp.len);
                        if (!cp)
                                goto free_and_fail1;
                        /* They must match, otherwise ignore */
                        if (strcmp(cp, first.buf))
                                goto free_and_fail1;
                        strbuf_release(&sp);
                        return strbuf_detach(&first, NULL);
                }

                /* unquoted second */
                cp = skip_tree_prefix(second, line + llen - second);
                if (!cp)
                        goto free_and_fail1;
                if (line + llen - cp != first.len ||
                    memcmp(first.buf, cp, first.len))
                        goto free_and_fail1;
                return strbuf_detach(&first, NULL);

        free_and_fail1:
                strbuf_release(&first);
                strbuf_release(&sp);
                return NULL;
        }

        /* unquoted first name */
        name = skip_tree_prefix(line, llen);
        if (!name)
                return NULL;

        /*
         * since the first name is unquoted, a dq if exists must be
         * the beginning of the second name.
         */
        for (second = name; second < line + llen; second++) {
                if (*second == '"') {
                        struct strbuf sp = STRBUF_INIT;
                        const char *np;

                        if (unquote_c_style(&sp, second, NULL))
                                goto free_and_fail2;

                        np = skip_tree_prefix(sp.buf, sp.len);
                        if (!np)
                                goto free_and_fail2;

                        len = sp.buf + sp.len - np;
                        if (len < second - name &&
                            !strncmp(np, name, len) &&
                            isspace(name[len])) {
                                /* Good */
                                strbuf_remove(&sp, 0, np - sp.buf);
                                return strbuf_detach(&sp, NULL);
                        }

                free_and_fail2:
                        strbuf_release(&sp);
                        return NULL;
                }
        }

        /*
         * Accept a name only if it shows up twice, exactly the same
         * form.
         */
        second = strchr(name, '\n');
        if (!second)
                return NULL;
        line_len = second - name;
        for (len = 0 ; ; len++) {
                switch (name[len]) {
                default:
                        continue;
                case '\n':
                        return NULL;
                case '\t': case ' ':
                        /*
                         * Is this the separator between the preimage
                         * and the postimage pathname?  Again, we are
                         * only interested in the case where there is
                         * no rename, as this is only to set def_name
                         * and a rename patch has the names elsewhere
                         * in an unambiguous form.
                         */
                        if (!name[len + 1])
                                return NULL; /* no postimage name */
                        second = skip_tree_prefix(name + len + 1,
                                                  line_len - (len + 1));
                        if (!second)
                                return NULL;
                        /*
                         * Does len bytes starting at "name" and "second"
                         * (that are separated by one HT or SP we just
                         * found) exactly match?
                         */
                        if (second[len] == '\n' && !strncmp(name, second, len))
                                return xmemdupz(name, len);
                }
        }
}

/* Verify that we recognize the lines following a git header */
static int parse_git_header(const char *line, int len, unsigned int size, struct patch *patch)
{
        unsigned long offset;

        /* A git diff has explicit new/delete information, so we don't guess */
        patch->is_new = 0;
        patch->is_delete = 0;

        /*
         * Some things may not have the old name in the
         * rest of the headers anywhere (pure mode changes,
         * or removing or adding empty files), so we get
         * the default name from the header.
         */
        patch->def_name = git_header_name(line, len);
        if (patch->def_name && root) {
                char *s = xstrfmt("%s%s", root, patch->def_name);
                free(patch->def_name);
                patch->def_name = s;
        }

        line += len;
        size -= len;
        linenr++;
        for (offset = len ; size > 0 ; offset += len, size -= len, line += len, linenr++) {
                static const struct opentry {
                        const char *str;
                        int (*fn)(const char *, struct patch *);
                } optable[] = {
                        { "@@ -", gitdiff_hdrend },
                        { "--- ", gitdiff_oldname },
                        { "+++ ", gitdiff_newname },
                        { "old mode ", gitdiff_oldmode },
                        { "new mode ", gitdiff_newmode },
                        { "deleted file mode ", gitdiff_delete },
                        { "new file mode ", gitdiff_newfile },
                        { "copy from ", gitdiff_copysrc },
                        { "copy to ", gitdiff_copydst },
                        { "rename old ", gitdiff_renamesrc },
                        { "rename new ", gitdiff_renamedst },
                        { "rename from ", gitdiff_renamesrc },
                        { "rename to ", gitdiff_renamedst },
                        { "similarity index ", gitdiff_similarity },
                        { "dissimilarity index ", gitdiff_dissimilarity },
                        { "index ", gitdiff_index },
                        { "", gitdiff_unrecognized },
                };
                int i;

                len = linelen(line, size);
                if (!len || line[len-1] != '\n')
                        break;
                for (i = 0; i < ARRAY_SIZE(optable); i++) {
                        const struct opentry *p = optable + i;
                        int oplen = strlen(p->str);
                        if (len < oplen || memcmp(p->str, line, oplen))
                                continue;
                        if (p->fn(line + oplen, patch) < 0)
                                return offset;
                        break;
                }
        }

        return offset;
}

static int parse_num(const char *line, unsigned long *p)
{
        char *ptr;

        if (!isdigit(*line))
                return 0;
        *p = strtoul(line, &ptr, 10);
        return ptr - line;
}

static int parse_range(const char *line, int len, int offset, const char *expect,
                       unsigned long *p1, unsigned long *p2)
{
        int digits, ex;

        if (offset < 0 || offset >= len)
                return -1;
        line += offset;
        len -= offset;

        digits = parse_num(line, p1);
        if (!digits)
                return -1;

        offset += digits;
        line += digits;
        len -= digits;

        *p2 = 1;
        if (*line == ',') {
                digits = parse_num(line+1, p2);
                if (!digits)
                        return -1;

                offset += digits+1;
                line += digits+1;
                len -= digits+1;
        }

        ex = strlen(expect);
        if (ex > len)
                return -1;
        if (memcmp(line, expect, ex))
                return -1;

        return offset + ex;
}

static void recount_diff(const char *line, int size, struct fragment *fragment)
{
        int oldlines = 0, newlines = 0, ret = 0;

        if (size < 1) {
                warning("recount: ignore empty hunk");
                return;
        }

        for (;;) {
                int len = linelen(line, size);
                size -= len;
                line += len;

                if (size < 1)
                        break;

                switch (*line) {
                case ' ': case '\n':
                        newlines++;
                        /* fall through */
                case '-':
                        oldlines++;
                        continue;
                case '+':
                        newlines++;
                        continue;
                case '\\':
                        continue;
                case '@':
                        ret = size < 3 || !starts_with(line, "@@ ");
                        break;
                case 'd':
                        ret = size < 5 || !starts_with(line, "diff ");
                        break;
                default:
                        ret = -1;
                        break;
                }
                if (ret) {
                        warning(_("recount: unexpected line: %.*s"),
                                (int)linelen(line, size), line);
                        return;
                }
                break;
        }
        fragment->oldlines = oldlines;
        fragment->newlines = newlines;
}

/*
 * Parse a unified diff fragment header of the
 * form "@@ -a,b +c,d @@"
 */
static int parse_fragment_header(const char *line, int len, struct fragment *fragment)
{
        int offset;

        if (!len || line[len-1] != '\n')
                return -1;

        /* Figure out the number of lines in a fragment */
        offset = parse_range(line, len, 4, " +", &fragment->oldpos, &fragment->oldlines);
        offset = parse_range(line, len, offset, " @@", &fragment->newpos, &fragment->newlines);

        return offset;
}

static int find_header(const char *line, unsigned long size, int *hdrsize, struct patch *patch)
{
        unsigned long offset, len;

        patch->is_toplevel_relative = 0;
        patch->is_rename = patch->is_copy = 0;
        patch->is_new = patch->is_delete = -1;
        patch->old_mode = patch->new_mode = 0;
        patch->old_name = patch->new_name = NULL;
        for (offset = 0; size > 0; offset += len, size -= len, line += len, linenr++) {
                unsigned long nextlen;

                len = linelen(line, size);
                if (!len)
                        break;

                /* Testing this early allows us to take a few shortcuts.. */
                if (len < 6)
                        continue;

                /*
                 * Make sure we don't find any unconnected patch fragments.
                 * That's a sign that we didn't find a header, and that a
                 * patch has become corrupted/broken up.
                 */
                if (!memcmp("@@ -", line, 4)) {
                        struct fragment dummy;
                        if (parse_fragment_header(line, len, &dummy) < 0)
                                continue;
                        die(_("patch fragment without header at line %d: %.*s"),
                            linenr, (int)len-1, line);
                }

                if (size < len + 6)
                        break;

                /*
                 * Git patch? It might not have a real patch, just a rename
                 * or mode change, so we handle that specially
                 */
                if (!memcmp("diff --git ", line, 11)) {
                        int git_hdr_len = parse_git_header(line, len, size, patch);
                        if (git_hdr_len <= len)
                                continue;
                        if (!patch->old_name && !patch->new_name) {
                                if (!patch->def_name)
                                        die(Q_("git diff header lacks filename information when removing "
                                               "%d leading pathname component (line %d)",
                                               "git diff header lacks filename information when removing "
                                               "%d leading pathname components (line %d)",
                                               p_value),
                                            p_value, linenr);
                                patch->old_name = xstrdup(patch->def_name);
                                patch->new_name = xstrdup(patch->def_name);
                        }
                        if (!patch->is_delete && !patch->new_name)
                                die("git diff header lacks filename information "
                                    "(line %d)", linenr);
                        patch->is_toplevel_relative = 1;
                        *hdrsize = git_hdr_len;
                        return offset;
                }

                /* --- followed by +++ ? */
                if (memcmp("--- ", line,  4) || memcmp("+++ ", line + len, 4))
                        continue;

                /*
                 * We only accept unified patches, so we want it to
                 * at least have "@@ -a,b +c,d @@\n", which is 14 chars
                 * minimum ("@@ -0,0 +1 @@\n" is the shortest).
                 */
                nextlen = linelen(line + len, size - len);
                if (size < nextlen + 14 || memcmp("@@ -", line + len + nextlen, 4))
                        continue;

                /* Ok, we'll consider it a patch */
                parse_traditional_patch(line, line+len, patch);
                *hdrsize = len + nextlen;
                linenr += 2;
                return offset;
        }
        return -1;
}

static void record_ws_error(unsigned result, const char *line, int len, int linenr)
{
        char *err;

        if (!result)
                return;

        whitespace_error++;
        if (squelch_whitespace_errors &&
            squelch_whitespace_errors < whitespace_error)
                return;

        err = whitespace_error_string(result);
        fprintf(stderr, "%s:%d: %s.\n%.*s\n",
                patch_input_file, linenr, err, len, line);
        free(err);
}

static void check_whitespace(const char *line, int len, unsigned ws_rule)
{
        unsigned result = ws_check(line + 1, len - 1, ws_rule);

        record_ws_error(result, line + 1, len - 2, linenr);
}

/*
 * Parse a unified diff. Note that this really needs to parse each
 * fragment separately, since the only way to know the difference
 * between a "---" that is part of a patch, and a "---" that starts
 * the next patch is to look at the line counts..
 */
static int parse_fragment(const char *line, unsigned long size,
                          struct patch *patch, struct fragment *fragment)
{
        int added, deleted;
        int len = linelen(line, size), offset;
        unsigned long oldlines, newlines;
        unsigned long leading, trailing;

        offset = parse_fragment_header(line, len, fragment);
        if (offset < 0)
                return -1;
        if (offset > 0 && patch->recount)
                recount_diff(line + offset, size - offset, fragment);
        oldlines = fragment->oldlines;
        newlines = fragment->newlines;
        leading = 0;
        trailing = 0;

        /* Parse the thing.. */
        line += len;
        size -= len;
        linenr++;
        added = deleted = 0;
        for (offset = len;
             0 < size;
             offset += len, size -= len, line += len, linenr++) {
                if (!oldlines && !newlines)
                        break;
                len = linelen(line, size);
                if (!len || line[len-1] != '\n')
                        return -1;
                switch (*line) {
                default:
                        return -1;
                case '\n': /* newer GNU diff, an empty context line */
                case ' ':
                        oldlines--;
                        newlines--;
                        if (!deleted && !added)
                                leading++;
                        trailing++;
                        break;
                case '-':
                        if (apply_in_reverse &&
                            ws_error_action != nowarn_ws_error)
                                check_whitespace(line, len, patch->ws_rule);
                        deleted++;
                        oldlines--;
                        trailing = 0;
                        break;
                case '+':
                        if (!apply_in_reverse &&
                            ws_error_action != nowarn_ws_error)
                                check_whitespace(line, len, patch->ws_rule);
                        added++;
                        newlines--;
                        trailing = 0;
                        break;

                /*
                 * We allow "\ No newline at end of file". Depending
                 * on locale settings when the patch was produced we
                 * don't know what this line looks like. The only
                 * thing we do know is that it begins with "\ ".
                 * Checking for 12 is just for sanity check -- any
                 * l10n of "\ No newline..." is at least that long.
                 */
                case '\\':
                        if (len < 12 || memcmp(line, "\\ ", 2))
                                return -1;
                        break;
                }
        }
        if (oldlines || newlines)
                return -1;
        fragment->leading = leading;
        fragment->trailing = trailing;

        /*
         * If a fragment ends with an incomplete line, we failed to include
         * it in the above loop because we hit oldlines == newlines == 0
         * before seeing it.
         */
        if (12 < size && !memcmp(line, "\\ ", 2))
                offset += linelen(line, size);

        patch->lines_added += added;
        patch->lines_deleted += deleted;

        if (0 < patch->is_new && oldlines)
                return error(_("new file depends on old contents"));
        if (0 < patch->is_delete && newlines)
                return error(_("deleted file still has contents"));
        return offset;
}

/*
 * We have seen "diff --git a/... b/..." header (or a traditional patch
 * header).  Read hunks that belong to this patch into fragments and hang
 * them to the given patch structure.
 *
 * The (fragment->patch, fragment->size) pair points into the memory given
 * by the caller, not a copy, when we return.
 */
static int parse_single_patch(const char *line, unsigned long size, struct patch *patch)
{
        unsigned long offset = 0;
        unsigned long oldlines = 0, newlines = 0, context = 0;
        struct fragment **fragp = &patch->fragments;

        while (size > 4 && !memcmp(line, "@@ -", 4)) {
                struct fragment *fragment;
                int len;

                fragment = xcalloc(1, sizeof(*fragment));
                fragment->linenr = linenr;
                len = parse_fragment(line, size, patch, fragment);
                if (len <= 0)
                        die(_("corrupt patch at line %d"), linenr);
                fragment->patch = line;
                fragment->size = len;
                oldlines += fragment->oldlines;
                newlines += fragment->newlines;
                context += fragment->leading + fragment->trailing;

                *fragp = fragment;
                fragp = &fragment->next;

                offset += len;
                line += len;
                size -= len;
        }

        /*
         * If something was removed (i.e. we have old-lines) it cannot
         * be creation, and if something was added it cannot be
         * deletion.  However, the reverse is not true; --unified=0
         * patches that only add are not necessarily creation even
         * though they do not have any old lines, and ones that only
         * delete are not necessarily deletion.
         *
         * Unfortunately, a real creation/deletion patch do _not_ have
         * any context line by definition, so we cannot safely tell it
         * apart with --unified=0 insanity.  At least if the patch has
         * more than one hunk it is not creation or deletion.
         */
        if (patch->is_new < 0 &&
            (oldlines || (patch->fragments && patch->fragments->next)))
                patch->is_new = 0;
        if (patch->is_delete < 0 &&
            (newlines || (patch->fragments && patch->fragments->next)))
                patch->is_delete = 0;

        if (0 < patch->is_new && oldlines)
                die(_("new file %s depends on old contents"), patch->new_name);
        if (0 < patch->is_delete && newlines)
                die(_("deleted file %s still has contents"), patch->old_name);
        if (!patch->is_delete && !newlines && context)
                fprintf_ln(stderr,
                           _("** warning: "
                             "file %s becomes empty but is not deleted"),
                           patch->new_name);

        return offset;
}

static inline int metadata_changes(struct patch *patch)
{
        return  patch->is_rename > 0 ||
                patch->is_copy > 0 ||
                patch->is_new > 0 ||
                patch->is_delete ||
                (patch->old_mode && patch->new_mode &&
                 patch->old_mode != patch->new_mode);
}

static char *inflate_it(const void *data, unsigned long size,
                        unsigned long inflated_size)
{
        git_zstream stream;
        void *out;
        int st;

        memset(&stream, 0, sizeof(stream));

        stream.next_in = (unsigned char *)data;
        stream.avail_in = size;
        stream.next_out = out = xmalloc(inflated_size);
        stream.avail_out = inflated_size;
        git_inflate_init(&stream);
        st = git_inflate(&stream, Z_FINISH);
        git_inflate_end(&stream);
        if ((st != Z_STREAM_END) || stream.total_out != inflated_size) {
                free(out);
                return NULL;
        }
        return out;
}

/*
 * Read a binary hunk and return a new fragment; fragment->patch
 * points at an allocated memory that the caller must free, so
 * it is marked as "->free_patch = 1".
 */
static struct fragment *parse_binary_hunk(char **buf_p,
                                          unsigned long *sz_p,
                                          int *status_p,
                                          int *used_p)
{
        /*
         * Expect a line that begins with binary patch method ("literal"
         * or "delta"), followed by the length of data before deflating.
         * a sequence of 'length-byte' followed by base-85 encoded data
         * should follow, terminated by a newline.
         *
         * Each 5-byte sequence of base-85 encodes up to 4 bytes,
         * and we would limit the patch line to 66 characters,
         * so one line can fit up to 13 groups that would decode
         * to 52 bytes max.  The length byte 'A'-'Z' corresponds
         * to 1-26 bytes, and 'a'-'z' corresponds to 27-52 bytes.
         */
        int llen, used;
        unsigned long size = *sz_p;
        char *buffer = *buf_p;
        int patch_method;
        unsigned long origlen;
        char *data = NULL;
        int hunk_size = 0;
        struct fragment *frag;

        llen = linelen(buffer, size);
        used = llen;

        *status_p = 0;

        if (starts_with(buffer, "delta ")) {
                patch_method = BINARY_DELTA_DEFLATED;
                origlen = strtoul(buffer + 6, NULL, 10);
        }
        else if (starts_with(buffer, "literal ")) {
                patch_method = BINARY_LITERAL_DEFLATED;
                origlen = strtoul(buffer + 8, NULL, 10);
        }
        else
                return NULL;

        linenr++;
        buffer += llen;
        while (1) {
                int byte_length, max_byte_length, newsize;
                llen = linelen(buffer, size);
                used += llen;
                linenr++;
                if (llen == 1) {
                        /* consume the blank line */
                        buffer++;
                        size--;
                        break;
                }
                /*
                 * Minimum line is "A00000\n" which is 7-byte long,
                 * and the line length must be multiple of 5 plus 2.
                 */
                if ((llen < 7) || (llen-2) % 5)
                        goto corrupt;
                max_byte_length = (llen - 2) / 5 * 4;
                byte_length = *buffer;
                if ('A' <= byte_length && byte_length <= 'Z')
                        byte_length = byte_length - 'A' + 1;
                else if ('a' <= byte_length && byte_length <= 'z')
                        byte_length = byte_length - 'a' + 27;
                else
                        goto corrupt;
                /* if the input length was not multiple of 4, we would
                 * have filler at the end but the filler should never
                 * exceed 3 bytes
                 */
                if (max_byte_length < byte_length ||
                    byte_length <= max_byte_length - 4)
                        goto corrupt;
                newsize = hunk_size + byte_length;
                data = xrealloc(data, newsize);
                if (decode_85(data + hunk_size, buffer + 1, byte_length))
                        goto corrupt;
                hunk_size = newsize;
                buffer += llen;
                size -= llen;
        }

        frag = xcalloc(1, sizeof(*frag));
        frag->patch = inflate_it(data, hunk_size, origlen);
        frag->free_patch = 1;
        if (!frag->patch)
                goto corrupt;
        free(data);
        frag->size = origlen;
        *buf_p = buffer;
        *sz_p = size;
        *used_p = used;
        frag->binary_patch_method = patch_method;
        return frag;

 corrupt:
        free(data);
        *status_p = -1;
        error(_("corrupt binary patch at line %d: %.*s"),
              linenr-1, llen-1, buffer);
        return NULL;
}

static int parse_binary(char *buffer, unsigned long size, struct patch *patch)
{
        /*
         * We have read "GIT binary patch\n"; what follows is a line
         * that says the patch method (currently, either "literal" or
         * "delta") and the length of data before deflating; a
         * sequence of 'length-byte' followed by base-85 encoded data
         * follows.
         *
         * When a binary patch is reversible, there is another binary
         * hunk in the same format, starting with patch method (either
         * "literal" or "delta") with the length of data, and a sequence
         * of length-byte + base-85 encoded data, terminated with another
         * empty line.  This data, when applied to the postimage, produces
         * the preimage.
         */
        struct fragment *forward;
        struct fragment *reverse;
        int status;
        int used, used_1;

        forward = parse_binary_hunk(&buffer, &size, &status, &used);
        if (!forward && !status)
                /* there has to be one hunk (forward hunk) */
                return error(_("unrecognized binary patch at line %d"), linenr-1);
        if (status)
                /* otherwise we already gave an error message */
                return status;

        reverse = parse_binary_hunk(&buffer, &size, &status, &used_1);
        if (reverse)
                used += used_1;
        else if (status) {
                /*
                 * Not having reverse hunk is not an error, but having
                 * a corrupt reverse hunk is.
                 */
                free((void*) forward->patch);
                free(forward);
                return status;
        }
        forward->next = reverse;
        patch->fragments = forward;
        patch->is_binary = 1;
        return used;
}

static void prefix_one(char **name)
{
        char *old_name = *name;
        if (!old_name)
                return;
        *name = xstrdup(prefix_filename(prefix, prefix_length, *name));
        free(old_name);
}

static void prefix_patch(struct patch *p)
{
        if (!prefix || p->is_toplevel_relative)
                return;
        prefix_one(&p->new_name);
        prefix_one(&p->old_name);
}

/*
 * include/exclude
 */

static struct string_list limit_by_name;
static int has_include;
static void add_name_limit(const char *name, int exclude)
{
        struct string_list_item *it;

        it = string_list_append(&limit_by_name, name);
        it->util = exclude ? NULL : (void *) 1;
}

static int use_patch(struct patch *p)
{
        const char *pathname = p->new_name ? p->new_name : p->old_name;
        int i;

        /* Paths outside are not touched regardless of "--include" */
        if (0 < prefix_length) {
                int pathlen = strlen(pathname);
                if (pathlen <= prefix_length ||
                    memcmp(prefix, pathname, prefix_length))
                        return 0;
        }

        /* See if it matches any of exclude/include rule */
        for (i = 0; i < limit_by_name.nr; i++) {
                struct string_list_item *it = &limit_by_name.items[i];
                if (!wildmatch(it->string, pathname, 0, NULL))
                        return (it->util != NULL);
        }

        /*
         * If we had any include, a path that does not match any rule is
         * not used.  Otherwise, we saw bunch of exclude rules (or none)
         * and such a path is used.
         */
        return !has_include;
}


/*
 * Read the patch text in "buffer" that extends for "size" bytes; stop
 * reading after seeing a single patch (i.e. changes to a single file).
 * Create fragments (i.e. patch hunks) and hang them to the given patch.
 * Return the number of bytes consumed, so that the caller can call us
 * again for the next patch.
 */
static int parse_chunk(char *buffer, unsigned long size, struct patch *patch)
{
        int hdrsize, patchsize;
        int offset = find_header(buffer, size, &hdrsize, patch);

        if (offset < 0)
                return offset;

        prefix_patch(patch);

        if (!use_patch(patch))
                patch->ws_rule = 0;
        else
                patch->ws_rule = whitespace_rule(patch->new_name
                                                 ? patch->new_name
                                                 : patch->old_name);

        patchsize = parse_single_patch(buffer + offset + hdrsize,
                                       size - offset - hdrsize, patch);

        if (!patchsize) {
                static const char git_binary[] = "GIT binary patch\n";
                int hd = hdrsize + offset;
                unsigned long llen = linelen(buffer + hd, size - hd);

                if (llen == sizeof(git_binary) - 1 &&
                    !memcmp(git_binary, buffer + hd, llen)) {
                        int used;
                        linenr++;
                        used = parse_binary(buffer + hd + llen,
                                            size - hd - llen, patch);
                        if (used)
                                patchsize = used + llen;
                        else
                                patchsize = 0;
                }
                else if (!memcmp(" differ\n", buffer + hd + llen - 8, 8)) {
                        static const char *binhdr[] = {
                                "Binary files ",
                                "Files ",
                                NULL,
                        };
                        int i;
                        for (i = 0; binhdr[i]; i++) {
                                int len = strlen(binhdr[i]);
                                if (len < size - hd &&
                                    !memcmp(binhdr[i], buffer + hd, len)) {
                                        linenr++;
                                        patch->is_binary = 1;
                                        patchsize = llen;
                                        break;
                                }
                        }
                }

                /* Empty patch cannot be applied if it is a text patch
                 * without metadata change.  A binary patch appears
                 * empty to us here.
                 */
                if ((apply || check) &&
                    (!patch->is_binary && !metadata_changes(patch)))
                        die(_("patch with only garbage at line %d"), linenr);
        }

        return offset + hdrsize + patchsize;
}

#define swap(a,b) myswap((a),(b),sizeof(a))

#define myswap(a, b, size) do {         \
        unsigned char mytmp[size];      \
        memcpy(mytmp, &a, size);                \
        memcpy(&a, &b, size);           \
        memcpy(&b, mytmp, size);                \
} while (0)

static void reverse_patches(struct patch *p)
{
        for (; p; p = p->next) {
                struct fragment *frag = p->fragments;

                swap(p->new_name, p->old_name);
                swap(p->new_mode, p->old_mode);
                swap(p->is_new, p->is_delete);
                swap(p->lines_added, p->lines_deleted);
                swap(p->old_sha1_prefix, p->new_sha1_prefix);

                for (; frag; frag = frag->next) {
                        swap(frag->newpos, frag->oldpos);
                        swap(frag->newlines, frag->oldlines);
                }
        }
}

static const char pluses[] =
"++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++";
static const char minuses[]=
"----------------------------------------------------------------------";

static void show_stats(struct patch *patch)
{
        struct strbuf qname = STRBUF_INIT;
        char *cp = patch->new_name ? patch->new_name : patch->old_name;
        int max, add, del;

        quote_c_style(cp, &qname, NULL, 0);

        /*
         * "scale" the filename
         */
        max = max_len;
        if (max > 50)
                max = 50;

        if (qname.len > max) {
                cp = strchr(qname.buf + qname.len + 3 - max, '/');
                if (!cp)
                        cp = qname.buf + qname.len + 3 - max;
                strbuf_splice(&qname, 0, cp - qname.buf, "...", 3);
        }

        if (patch->is_binary) {
                printf(" %-*s |  Bin\n", max, qname.buf);
                strbuf_release(&qname);
                return;
        }

        printf(" %-*s |", max, qname.buf);
        strbuf_release(&qname);

        /*
         * scale the add/delete
         */
        max = max + max_change > 70 ? 70 - max : max_change;
        add = patch->lines_added;
        del = patch->lines_deleted;

        if (max_change > 0) {
                int total = ((add + del) * max + max_change / 2) / max_change;
                add = (add * max + max_change / 2) / max_change;
                del = total - add;
        }
        printf("%5d %.*s%.*s\n", patch->lines_added + patch->lines_deleted,
                add, pluses, del, minuses);
}

static int read_old_data(struct stat *st, const char *path, struct strbuf *buf)
{
        switch (st->st_mode & S_IFMT) {
        case S_IFLNK:
                if (strbuf_readlink(buf, path, st->st_size) < 0)
                        return error(_("unable to read symlink %s"), path);
                return 0;
        case S_IFREG:
                if (strbuf_read_file(buf, path, st->st_size) != st->st_size)
                        return error(_("unable to open or read %s"), path);
                convert_to_git(path, buf->buf, buf->len, buf, 0);
                return 0;
        default:
                return -1;
        }
}

/*
 * Update the preimage, and the common lines in postimage,
 * from buffer buf of length len. If postlen is 0 the postimage
 * is updated in place, otherwise it's updated on a new buffer
 * of length postlen
 */

static void update_pre_post_images(struct image *preimage,
                                   struct image *postimage,
                                   char *buf,
                                   size_t len, size_t postlen)
{
        int i, ctx, reduced;
        char *new, *old, *fixed;
        struct image fixed_preimage;

        /*
         * Update the preimage with whitespace fixes.  Note that we
         * are not losing preimage->buf -- apply_one_fragment() will
         * free "oldlines".
         */
        prepare_image(&fixed_preimage, buf, len, 1);
        assert(postlen
               ? fixed_preimage.nr == preimage->nr
               : fixed_preimage.nr <= preimage->nr);
        for (i = 0; i < fixed_preimage.nr; i++)
                fixed_preimage.line[i].flag = preimage->line[i].flag;
        free(preimage->line_allocated);
        *preimage = fixed_preimage;

        /*
         * Adjust the common context lines in postimage. This can be
         * done in-place when we are shrinking it with whitespace
         * fixing, but needs a new buffer when ignoring whitespace or
         * expanding leading tabs to spaces.
         *
         * We trust the caller to tell us if the update can be done
         * in place (postlen==0) or not.
         */
        old = postimage->buf;
        if (postlen)
                new = postimage->buf = xmalloc(postlen);
        else
                new = old;
        fixed = preimage->buf;

        for (i = reduced = ctx = 0; i < postimage->nr; i++) {
                size_t len = postimage->line[i].len;
                if (!(postimage->line[i].flag & LINE_COMMON)) {
                        /* an added line -- no counterparts in preimage */
                        memmove(new, old, len);
                        old += len;
                        new += len;
                        continue;
                }

                /* a common context -- skip it in the original postimage */
                old += len;

                /* and find the corresponding one in the fixed preimage */
                while (ctx < preimage->nr &&
                       !(preimage->line[ctx].flag & LINE_COMMON)) {
                        fixed += preimage->line[ctx].len;
                        ctx++;
                }

                /*
                 * preimage is expected to run out, if the caller
                 * fixed addition of trailing blank lines.
                 */
                if (preimage->nr <= ctx) {
                        reduced++;
                        continue;
                }

                /* and copy it in, while fixing the line length */
                len = preimage->line[ctx].len;
                memcpy(new, fixed, len);
                new += len;
                fixed += len;
                postimage->line[i].len = len;
                ctx++;
        }

        /* Fix the length of the whole thing */
        postimage->len = new - postimage->buf;
        postimage->nr -= reduced;
}

static int match_fragment(struct image *img,
                          struct image *preimage,
                          struct image *postimage,
                          unsigned long try,
                          int try_lno,
                          unsigned ws_rule,
                          int match_beginning, int match_end)
{
        int i;
        char *fixed_buf, *buf, *orig, *target;
        struct strbuf fixed;
        size_t fixed_len, postlen;
        int preimage_limit;

        if (preimage->nr + try_lno <= img->nr) {
                /*
                 * The hunk falls within the boundaries of img.
                 */
                preimage_limit = preimage->nr;
                if (match_end && (preimage->nr + try_lno != img->nr))
                        return 0;
        } else if (ws_error_action == correct_ws_error &&
                   (ws_rule & WS_BLANK_AT_EOF)) {
                /*
                 * This hunk extends beyond the end of img, and we are
                 * removing blank lines at the end of the file.  This
                 * many lines from the beginning of the preimage must
                 * match with img, and the remainder of the preimage
                 * must be blank.
                 */
                preimage_limit = img->nr - try_lno;
        } else {
                /*
                 * The hunk extends beyond the end of the img and
                 * we are not removing blanks at the end, so we
                 * should reject the hunk at this position.
                 */
                return 0;
        }

        if (match_beginning && try_lno)
                return 0;

        /* Quick hash check */
        for (i = 0; i < preimage_limit; i++)
                if ((img->line[try_lno + i].flag & LINE_PATCHED) ||
                    (preimage->line[i].hash != img->line[try_lno + i].hash))
                        return 0;

        if (preimage_limit == preimage->nr) {
                /*
                 * Do we have an exact match?  If we were told to match
                 * at the end, size must be exactly at try+fragsize,
                 * otherwise try+fragsize must be still within the preimage,
                 * and either case, the old piece should match the preimage
                 * exactly.
                 */
                if ((match_end
                     ? (try + preimage->len == img->len)
                     : (try + preimage->len <= img->len)) &&
                    !memcmp(img->buf + try, preimage->buf, preimage->len))
                        return 1;
        } else {
                /*
                 * The preimage extends beyond the end of img, so
                 * there cannot be an exact match.
                 *
                 * There must be one non-blank context line that match
                 * a line before the end of img.
                 */
                char *buf_end;

                buf = preimage->buf;
                buf_end = buf;
                for (i = 0; i < preimage_limit; i++)
                        buf_end += preimage->line[i].len;

                for ( ; buf < buf_end; buf++)
                        if (!isspace(*buf))
                                break;
                if (buf == buf_end)
                        return 0;
        }

        /*
         * No exact match. If we are ignoring whitespace, run a line-by-line
         * fuzzy matching. We collect all the line length information because
         * we need it to adjust whitespace if we match.
         */
        if (ws_ignore_action == ignore_ws_change) {
                size_t imgoff = 0;
                size_t preoff = 0;
                size_t postlen = postimage->len;
                size_t extra_chars;
                char *preimage_eof;
                char *preimage_end;
                for (i = 0; i < preimage_limit; i++) {
                        size_t prelen = preimage->line[i].len;
                        size_t imglen = img->line[try_lno+i].len;

                        if (!fuzzy_matchlines(img->buf + try + imgoff, imglen,
                                              preimage->buf + preoff, prelen))
                                return 0;
                        if (preimage->line[i].flag & LINE_COMMON)
                                postlen += imglen - prelen;
                        imgoff += imglen;
                        preoff += prelen;
                }

                /*
                 * Ok, the preimage matches with whitespace fuzz.
                 *
                 * imgoff now holds the true length of the target that
                 * matches the preimage before the end of the file.
                 *
                 * Count the number of characters in the preimage that fall
                 * beyond the end of the file and make sure that all of them
                 * are whitespace characters. (This can only happen if
                 * we are removing blank lines at the end of the file.)
                 */
                buf = preimage_eof = preimage->buf + preoff;
                for ( ; i < preimage->nr; i++)
                        preoff += preimage->line[i].len;
                preimage_end = preimage->buf + preoff;
                for ( ; buf < preimage_end; buf++)
                        if (!isspace(*buf))
                                return 0;

                /*
                 * Update the preimage and the common postimage context
                 * lines to use the same whitespace as the target.
                 * If whitespace is missing in the target (i.e.
                 * if the preimage extends beyond the end of the file),
                 * use the whitespace from the preimage.
                 */
                extra_chars = preimage_end - preimage_eof;
                strbuf_init(&fixed, imgoff + extra_chars);
                strbuf_add(&fixed, img->buf + try, imgoff);
                strbuf_add(&fixed, preimage_eof, extra_chars);
                fixed_buf = strbuf_detach(&fixed, &fixed_len);
                update_pre_post_images(preimage, postimage,
                                fixed_buf, fixed_len, postlen);
                return 1;
        }

        if (ws_error_action != correct_ws_error)
                return 0;

        /*
         * The hunk does not apply byte-by-byte, but the hash says
         * it might with whitespace fuzz. We haven't been asked to
         * ignore whitespace, we were asked to correct whitespace
         * errors, so let's try matching after whitespace correction.
         *
         * The preimage may extend beyond the end of the file,
         * but in this loop we will only handle the part of the
         * preimage that falls within the file.
         */
        strbuf_init(&fixed, preimage->len + 1);
        orig = preimage->buf;
        target = img->buf + try;
        postlen = 0;
        for (i = 0; i < preimage_limit; i++) {
                size_t oldlen = preimage->line[i].len;
                size_t tgtlen = img->line[try_lno + i].len;
                size_t fixstart = fixed.len;
                struct strbuf tgtfix;
                int match;

                /* Try fixing the line in the preimage */
                ws_fix_copy(&fixed, orig, oldlen, ws_rule, NULL);

                /* Try fixing the line in the target */
                strbuf_init(&tgtfix, tgtlen);
                ws_fix_copy(&tgtfix, target, tgtlen, ws_rule, NULL);

                /*
                 * If they match, either the preimage was based on
                 * a version before our tree fixed whitespace breakage,
                 * or we are lacking a whitespace-fix patch the tree
                 * the preimage was based on already had (i.e. target
                 * has whitespace breakage, the preimage doesn't).
                 * In either case, we are fixing the whitespace breakages
                 * so we might as well take the fix together with their
                 * real change.
                 */
                match = (tgtfix.len == fixed.len - fixstart &&
                         !memcmp(tgtfix.buf, fixed.buf + fixstart,
                                             fixed.len - fixstart));
                postlen += tgtfix.len;

                strbuf_release(&tgtfix);
                if (!match)
                        goto unmatch_exit;

                orig += oldlen;
                target += tgtlen;
        }


        /*
         * Now handle the lines in the preimage that falls beyond the
         * end of the file (if any). They will only match if they are
         * empty or only contain whitespace (if WS_BLANK_AT_EOL is
         * false).
         */
        for ( ; i < preimage->nr; i++) {
                size_t fixstart = fixed.len; /* start of the fixed preimage */
                size_t oldlen = preimage->line[i].len;
                int j;

                /* Try fixing the line in the preimage */
                ws_fix_copy(&fixed, orig, oldlen, ws_rule, NULL);

                for (j = fixstart; j < fixed.len; j++)
                        if (!isspace(fixed.buf[j]))
                                goto unmatch_exit;

                orig += oldlen;
        }

        /*
         * Yes, the preimage is based on an older version that still
         * has whitespace breakages unfixed, and fixing them makes the
         * hunk match.  Update the context lines in the postimage.
         */
        fixed_buf = strbuf_detach(&fixed, &fixed_len);
        if (postlen < postimage->len)
                postlen = 0;
        update_pre_post_images(preimage, postimage,
                               fixed_buf, fixed_len, postlen);
        return 1;

 unmatch_exit:
        strbuf_release(&fixed);
        return 0;
}

static int find_pos(struct image *img,
                    struct image *preimage,
                    struct image *postimage,
                    int line,
                    unsigned ws_rule,
                    int match_beginning, int match_end)
{
        int i;
        unsigned long backwards, forwards, try;
        int backwards_lno, forwards_lno, try_lno;

        /*
         * If match_beginning or match_end is specified, there is no
         * point starting from a wrong line that will never match and
         * wander around and wait for a match at the specified end.
         */
        if (match_beginning)
                line = 0;
        else if (match_end)
                line = img->nr - preimage->nr;

        /*
         * Because the comparison is unsigned, the following test
         * will also take care of a negative line number that can
         * result when match_end and preimage is larger than the target.
         */
        if ((size_t) line > img->nr)
                line = img->nr;

        try = 0;
        for (i = 0; i < line; i++)
                try += img->line[i].len;

        /*
         * There's probably some smart way to do this, but I'll leave
         * that to the smart and beautiful people. I'm simple and stupid.
         */
        backwards = try;
        backwards_lno = line;
        forwards = try;
        forwards_lno = line;
        try_lno = line;

        for (i = 0; ; i++) {
                if (match_fragment(img, preimage, postimage,
                                   try, try_lno, ws_rule,
                                   match_beginning, match_end))
                        return try_lno;

        again:
                if (backwards_lno == 0 && forwards_lno == img->nr)
                        break;

                if (i & 1) {
                        if (backwards_lno == 0) {
                                i++;
                                goto again;
                        }
                        backwards_lno--;
                        backwards -= img->line[backwards_lno].len;
                        try = backwards;
                        try_lno = backwards_lno;
                } else {
                        if (forwards_lno == img->nr) {
                                i++;
                                goto again;
                        }
                        forwards += img->line[forwards_lno].len;
                        forwards_lno++;
                        try = forwards;
                        try_lno = forwards_lno;
                }

        }
        return -1;
}

static void remove_first_line(struct image *img)
{
        img->buf += img->line[0].len;
        img->len -= img->line[0].len;
        img->line++;
        img->nr--;
}

static void remove_last_line(struct image *img)
{
        img->len -= img->line[--img->nr].len;
}

/*
 * The change from "preimage" and "postimage" has been found to
 * apply at applied_pos (counts in line numbers) in "img".
 * Update "img" to remove "preimage" and replace it with "postimage".
 */
static void update_image(struct image *img,
                         int applied_pos,
                         struct image *preimage,
                         struct image *postimage)
{
        /*
         * remove the copy of preimage at offset in img
         * and replace it with postimage
         */
        int i, nr;
        size_t remove_count, insert_count, applied_at = 0;
        char *result;
        int preimage_limit;

        /*
         * If we are removing blank lines at the end of img,
         * the preimage may extend beyond the end.
         * If that is the case, we must be careful only to
         * remove the part of the preimage that falls within
         * the boundaries of img. Initialize preimage_limit
         * to the number of lines in the preimage that falls
         * within the boundaries.
         */
        preimage_limit = preimage->nr;
        if (preimage_limit > img->nr - applied_pos)
                preimage_limit = img->nr - applied_pos;

        for (i = 0; i < applied_pos; i++)
                applied_at += img->line[i].len;

        remove_count = 0;
        for (i = 0; i < preimage_limit; i++)
                remove_count += img->line[applied_pos + i].len;
        insert_count = postimage->len;

        /* Adjust the contents */
        result = xmalloc(img->len + insert_count - remove_count + 1);
        memcpy(result, img->buf, applied_at);
        memcpy(result + applied_at, postimage->buf, postimage->len);
        memcpy(result + applied_at + postimage->len,
               img->buf + (applied_at + remove_count),
               img->len - (applied_at + remove_count));
        free(img->buf);
        img->buf = result;
        img->len += insert_count - remove_count;
        result[img->len] = '\0';

        /* Adjust the line table */
        nr = img->nr + postimage->nr - preimage_limit;
        if (preimage_limit < postimage->nr) {
                /*
                 * NOTE: this knows that we never call remove_first_line()
                 * on anything other than pre/post image.
                 */
                img->line = xrealloc(img->line, nr * sizeof(*img->line));
                img->line_allocated = img->line;
        }
        if (preimage_limit != postimage->nr)
                memmove(img->line + applied_pos + postimage->nr,
                        img->line + applied_pos + preimage_limit,
                        (img->nr - (applied_pos + preimage_limit)) *
                        sizeof(*img->line));
        memcpy(img->line + applied_pos,
               postimage->line,
               postimage->nr * sizeof(*img->line));
        if (!allow_overlap)
                for (i = 0; i < postimage->nr; i++)
                        img->line[applied_pos + i].flag |= LINE_PATCHED;
        img->nr = nr;
}

/*
 * Use the patch-hunk text in "frag" to prepare two images (preimage and
 * postimage) for the hunk.  Find lines that match "preimage" in "img" and
 * replace the part of "img" with "postimage" text.
 */
static int apply_one_fragment(struct image *img, struct fragment *frag,
                              int inaccurate_eof, unsigned ws_rule,
                              int nth_fragment)
{
        int match_beginning, match_end;
        const char *patch = frag->patch;
        int size = frag->size;
        char *old, *oldlines;
        struct strbuf newlines;
        int new_blank_lines_at_end = 0;
        int found_new_blank_lines_at_end = 0;
        int hunk_linenr = frag->linenr;
        unsigned long leading, trailing;
        int pos, applied_pos;
        struct image preimage;
        struct image postimage;

        memset(&preimage, 0, sizeof(preimage));
        memset(&postimage, 0, sizeof(postimage));
        oldlines = xmalloc(size);
        strbuf_init(&newlines, size);

        old = oldlines;
        while (size > 0) {
                char first;
                int len = linelen(patch, size);
                int plen;
                int added_blank_line = 0;
                int is_blank_context = 0;
                size_t start;

                if (!len)
                        break;

                /*
                 * "plen" is how much of the line we should use for
                 * the actual patch data. Normally we just remove the
                 * first character on the line, but if the line is
                 * followed by "\ No newline", then we also remove the
                 * last one (which is the newline, of course).
                 */
                plen = len - 1;
                if (len < size && patch[len] == '\\')
                        plen--;
                first = *patch;
                if (apply_in_reverse) {
                        if (first == '-')
                                first = '+';
                        else if (first == '+')
                                first = '-';
                }

                switch (first) {
                case '\n':
                        /* Newer GNU diff, empty context line */
                        if (plen < 0)
                                /* ... followed by '\No newline'; nothing */
                                break;
                        *old++ = '\n';
                        strbuf_addch(&newlines, '\n');
                        add_line_info(&preimage, "\n", 1, LINE_COMMON);
                        add_line_info(&postimage, "\n", 1, LINE_COMMON);
                        is_blank_context = 1;
                        break;
                case ' ':
                        if (plen && (ws_rule & WS_BLANK_AT_EOF) &&
                            ws_blank_line(patch + 1, plen, ws_rule))
                                is_blank_context = 1;
                case '-':
                        memcpy(old, patch + 1, plen);
                        add_line_info(&preimage, old, plen,
                                      (first == ' ' ? LINE_COMMON : 0));
                        old += plen;
                        if (first == '-')
                                break;
                /* Fall-through for ' ' */
                case '+':
                        /* --no-add does not add new lines */
                        if (first == '+' && no_add)
                                break;

                        start = newlines.len;
                        if (first != '+' ||
                            !whitespace_error ||
                            ws_error_action != correct_ws_error) {
                                strbuf_add(&newlines, patch + 1, plen);
                        }
                        else {
                                ws_fix_copy(&newlines, patch + 1, plen, ws_rule, &applied_after_fixing_ws);
                        }
                        add_line_info(&postimage, newlines.buf + start, newlines.len - start,
                                      (first == '+' ? 0 : LINE_COMMON));
                        if (first == '+' &&
                            (ws_rule & WS_BLANK_AT_EOF) &&
                            ws_blank_line(patch + 1, plen, ws_rule))
                                added_blank_line = 1;
                        break;
                case '@': case '\\':
                        /* Ignore it, we already handled it */
                        break;
                default:
                        if (apply_verbosely)
                                error(_("invalid start of line: '%c'"), first);
                        return -1;
                }
                if (added_blank_line) {
                        if (!new_blank_lines_at_end)
                                found_new_blank_lines_at_end = hunk_linenr;
                        new_blank_lines_at_end++;
                }
                else if (is_blank_context)
                        ;
                else
                        new_blank_lines_at_end = 0;
                patch += len;
                size -= len;
                hunk_linenr++;
        }
        if (inaccurate_eof &&
            old > oldlines && old[-1] == '\n' &&
            newlines.len > 0 && newlines.buf[newlines.len - 1] == '\n') {
                old--;
                strbuf_setlen(&newlines, newlines.len - 1);
        }

        leading = frag->leading;
        trailing = frag->trailing;

        /*
         * A hunk to change lines at the beginning would begin with
         * @@ -1,L +N,M @@
         * but we need to be careful.  -U0 that inserts before the second
         * line also has this pattern.
         *
         * And a hunk to add to an empty file would begin with
         * @@ -0,0 +N,M @@
         *
         * In other words, a hunk that is (frag->oldpos <= 1) with or
         * without leading context must match at the beginning.
         */
        match_beginning = (!frag->oldpos ||
                           (frag->oldpos == 1 && !unidiff_zero));

        /*
         * A hunk without trailing lines must match at the end.
         * However, we simply cannot tell if a hunk must match end
         * from the lack of trailing lines if the patch was generated
         * with unidiff without any context.
         */
        match_end = !unidiff_zero && !trailing;

        pos = frag->newpos ? (frag->newpos - 1) : 0;
        preimage.buf = oldlines;
        preimage.len = old - oldlines;
        postimage.buf = newlines.buf;
        postimage.len = newlines.len;
        preimage.line = preimage.line_allocated;
        postimage.line = postimage.line_allocated;

        for (;;) {

                applied_pos = find_pos(img, &preimage, &postimage, pos,
                                       ws_rule, match_beginning, match_end);

                if (applied_pos >= 0)
                        break;

                /* Am I at my context limits? */
                if ((leading <= p_context) && (trailing <= p_context))
                        break;
                if (match_beginning || match_end) {
                        match_beginning = match_end = 0;
                        continue;
                }

                /*
                 * Reduce the number of context lines; reduce both
                 * leading and trailing if they are equal otherwise
                 * just reduce the larger context.
                 */
                if (leading >= trailing) {
                        remove_first_line(&preimage);
                        remove_first_line(&postimage);
                        pos--;
                        leading--;
                }
                if (trailing > leading) {
                        remove_last_line(&preimage);
                        remove_last_line(&postimage);
                        trailing--;
                }
        }

        if (applied_pos >= 0) {
                if (new_blank_lines_at_end &&
                    preimage.nr + applied_pos >= img->nr &&
                    (ws_rule & WS_BLANK_AT_EOF) &&
                    ws_error_action != nowarn_ws_error) {
                        record_ws_error(WS_BLANK_AT_EOF, "+", 1,
                                        found_new_blank_lines_at_end);
                        if (ws_error_action == correct_ws_error) {
                                while (new_blank_lines_at_end--)
                                        remove_last_line(&postimage);
                        }
                        /*
                         * We would want to prevent write_out_results()
                         * from taking place in apply_patch() that follows
                         * the callchain led us here, which is:
                         * apply_patch->check_patch_list->check_patch->
                         * apply_data->apply_fragments->apply_one_fragment
                         */
                        if (ws_error_action == die_on_ws_error)
                                apply = 0;
                }

                if (apply_verbosely && applied_pos != pos) {
                        int offset = applied_pos - pos;
                        if (apply_in_reverse)
                                offset = 0 - offset;
                        fprintf_ln(stderr,
                                   Q_("Hunk #%d succeeded at %d (offset %d line).",
                                      "Hunk #%d succeeded at %d (offset %d lines).",
                                      offset),
                                   nth_fragment, applied_pos + 1, offset);
                }

                /*
                 * Warn if it was necessary to reduce the number
                 * of context lines.
                 */
                if ((leading != frag->leading) ||
                    (trailing != frag->trailing))
                        fprintf_ln(stderr, _("Context reduced to (%ld/%ld)"
                                             " to apply fragment at %d"),
                                   leading, trailing, applied_pos+1);
                update_image(img, applied_pos, &preimage, &postimage);
        } else {
                if (apply_verbosely)
                        error(_("while searching for:\n%.*s"),
                              (int)(old - oldlines), oldlines);
        }

        free(oldlines);
        strbuf_release(&newlines);
        free(preimage.line_allocated);
        free(postimage.line_allocated);

        return (applied_pos < 0);
}

static int apply_binary_fragment(struct image *img, struct patch *patch)
{
        struct fragment *fragment = patch->fragments;
        unsigned long len;
        void *dst;

        if (!fragment)
                return error(_("missing binary patch data for '%s'"),
                             patch->new_name ?
                             patch->new_name :
                             patch->old_name);

        /* Binary patch is irreversible without the optional second hunk */
        if (apply_in_reverse) {
                if (!fragment->next)
                        return error("cannot reverse-apply a binary patch "
                                     "without the reverse hunk to '%s'",
                                     patch->new_name
                                     ? patch->new_name : patch->old_name);
                fragment = fragment->next;
        }
        switch (fragment->binary_patch_method) {
        case BINARY_DELTA_DEFLATED:
                dst = patch_delta(img->buf, img->len, fragment->patch,
                                  fragment->size, &len);
                if (!dst)
                        return -1;
                clear_image(img);
                img->buf = dst;
                img->len = len;
                return 0;
        case BINARY_LITERAL_DEFLATED:
                clear_image(img);
                img->len = fragment->size;
                img->buf = xmemdupz(fragment->patch, img->len);
                return 0;
        }
        return -1;
}

/*
 * Replace "img" with the result of applying the binary patch.
 * The binary patch data itself in patch->fragment is still kept
 * but the preimage prepared by the caller in "img" is freed here
 * or in the helper function apply_binary_fragment() this calls.
 */
static int apply_binary(struct image *img, struct patch *patch)
{
        const char *name = patch->old_name ? patch->old_name : patch->new_name;
        unsigned char sha1[20];

        /*
         * For safety, we require patch index line to contain
         * full 40-byte textual SHA1 for old and new, at least for now.
         */
        if (strlen(patch->old_sha1_prefix) != 40 ||
            strlen(patch->new_sha1_prefix) != 40 ||
            get_sha1_hex(patch->old_sha1_prefix, sha1) ||
            get_sha1_hex(patch->new_sha1_prefix, sha1))
                return error("cannot apply binary patch to '%s' "
                             "without full index line", name);

        if (patch->old_name) {
                /*
                 * See if the old one matches what the patch
                 * applies to.
                 */
                hash_sha1_file(img->buf, img->len, blob_type, sha1);
                if (strcmp(sha1_to_hex(sha1), patch->old_sha1_prefix))
                        return error("the patch applies to '%s' (%s), "
                                     "which does not match the "
                                     "current contents.",
                                     name, sha1_to_hex(sha1));
        }
        else {
                /* Otherwise, the old one must be empty. */
                if (img->len)
                        return error("the patch applies to an empty "
                                     "'%s' but it is not empty", name);
        }

        get_sha1_hex(patch->new_sha1_prefix, sha1);
        if (is_null_sha1(sha1)) {
                clear_image(img);
                return 0; /* deletion patch */
        }

        if (has_sha1_file(sha1)) {
                /* We already have the postimage */
                enum object_type type;
                unsigned long size;
                char *result;

                result = read_sha1_file(sha1, &type, &size);
                if (!result)
                        return error("the necessary postimage %s for "
                                     "'%s' cannot be read",
                                     patch->new_sha1_prefix, name);
                clear_image(img);
                img->buf = result;
                img->len = size;
        } else {
                /*
                 * We have verified buf matches the preimage;
                 * apply the patch data to it, which is stored
                 * in the patch->fragments->{patch,size}.
                 */
                if (apply_binary_fragment(img, patch))
                        return error(_("binary patch does not apply to '%s'"),
                                     name);

                /* verify that the result matches */
                hash_sha1_file(img->buf, img->len, blob_type, sha1);
                if (strcmp(sha1_to_hex(sha1), patch->new_sha1_prefix))
                        return error(_("binary patch to '%s' creates incorrect result (expecting %s, got %s)"),
                                name, patch->new_sha1_prefix, sha1_to_hex(sha1));
        }

        return 0;
}

static int apply_fragments(struct image *img, struct patch *patch)
{
        struct fragment *frag = patch->fragments;
        const char *name = patch->old_name ? patch->old_name : patch->new_name;
        unsigned ws_rule = patch->ws_rule;
        unsigned inaccurate_eof = patch->inaccurate_eof;
        int nth = 0;

        if (patch->is_binary)
                return apply_binary(img, patch);

        while (frag) {
                nth++;
                if (apply_one_fragment(img, frag, inaccurate_eof, ws_rule, nth)) {
                        error(_("patch failed: %s:%ld"), name, frag->oldpos);
                        if (!apply_with_reject)
                                return -1;
                        frag->rejected = 1;
                }
                frag = frag->next;
        }
        return 0;
}

static int read_blob_object(struct strbuf *buf, const unsigned char *sha1, unsigned mode)
{
        if (S_ISGITLINK(mode)) {
                strbuf_grow(buf, 100);
                strbuf_addf(buf, "Subproject commit %s\n", sha1_to_hex(sha1));
        } else {
                enum object_type type;
                unsigned long sz;
                char *result;

                result = read_sha1_file(sha1, &type, &sz);
                if (!result)
                        return -1;
                /* XXX read_sha1_file NUL-terminates */
                strbuf_attach(buf, result, sz, sz + 1);
        }
        return 0;
}

static int read_file_or_gitlink(const struct cache_entry *ce, struct strbuf *buf)
{
        if (!ce)
                return 0;
        return read_blob_object(buf, ce->sha1, ce->ce_mode);
}

static struct patch *in_fn_table(const char *name)
{
        struct string_list_item *item;

        if (name == NULL)
                return NULL;

        item = string_list_lookup(&fn_table, name);
        if (item != NULL)
                return (struct patch *)item->util;

        return NULL;
}

/*
 * item->util in the filename table records the status of the path.
 * Usually it points at a patch (whose result records the contents
 * of it after applying it), but it could be PATH_WAS_DELETED for a
 * path that a previously applied patch has already removed, or
 * PATH_TO_BE_DELETED for a path that a later patch would remove.
 *
 * The latter is needed to deal with a case where two paths A and B
 * are swapped by first renaming A to B and then renaming B to A;
 * moving A to B should not be prevented due to presence of B as we
 * will remove it in a later patch.
 */
#define PATH_TO_BE_DELETED ((struct patch *) -2)
#define PATH_WAS_DELETED ((struct patch *) -1)

static int to_be_deleted(struct patch *patch)
{
        return patch == PATH_TO_BE_DELETED;
}

static int was_deleted(struct patch *patch)
{
        return patch == PATH_WAS_DELETED;
}

static void add_to_fn_table(struct patch *patch)
{
        struct string_list_item *item;

        /*
         * Always add new_name unless patch is a deletion
         * This should cover the cases for normal diffs,
         * file creations and copies
         */
        if (patch->new_name != NULL) {
                item = string_list_insert(&fn_table, patch->new_name);
                item->util = patch;
        }

        /*
         * store a failure on rename/deletion cases because
         * later chunks shouldn't patch old names
         */
        if ((patch->new_name == NULL) || (patch->is_rename)) {
                item = string_list_insert(&fn_table, patch->old_name);
                item->util = PATH_WAS_DELETED;
        }
}

static void prepare_fn_table(struct patch *patch)
{
        /*
         * store information about incoming file deletion
         */
        while (patch) {
                if ((patch->new_name == NULL) || (patch->is_rename)) {
                        struct string_list_item *item;
                        item = string_list_insert(&fn_table, patch->old_name);
                        item->util = PATH_TO_BE_DELETED;
                }
                patch = patch->next;
        }
}

static int checkout_target(struct index_state *istate,
                           struct cache_entry *ce, struct stat *st)
{
        struct checkout costate;

        memset(&costate, 0, sizeof(costate));
        costate.base_dir = "";
        costate.refresh_cache = 1;
        costate.istate = istate;
        if (checkout_entry(ce, &costate, NULL) || lstat(ce->name, st))
                return error(_("cannot checkout %s"), ce->name);
        return 0;
}

static struct patch *previous_patch(struct patch *patch, int *gone)
{
        struct patch *previous;

        *gone = 0;
        if (patch->is_copy || patch->is_rename)
                return NULL; /* "git" patches do not depend on the order */

        previous = in_fn_table(patch->old_name);
        if (!previous)
                return NULL;

        if (to_be_deleted(previous))
                return NULL; /* the deletion hasn't happened yet */

        if (was_deleted(previous))
                *gone = 1;

        return previous;
}

static int verify_index_match(const struct cache_entry *ce, struct stat *st)
{
        if (S_ISGITLINK(ce->ce_mode)) {
                if (!S_ISDIR(st->st_mode))
                        return -1;
                return 0;
        }
        return ce_match_stat(ce, st, CE_MATCH_IGNORE_VALID|CE_MATCH_IGNORE_SKIP_WORKTREE);
}

#define SUBMODULE_PATCH_WITHOUT_INDEX 1

static int load_patch_target(struct strbuf *buf,
                             const struct cache_entry *ce,
                             struct stat *st,
                             const char *name,
                             unsigned expected_mode)
{
        if (cached) {
                if (read_file_or_gitlink(ce, buf))
                        return error(_("read of %s failed"), name);
        } else if (name) {
                if (S_ISGITLINK(expected_mode)) {
                        if (ce)
                                return read_file_or_gitlink(ce, buf);
                        else
                                return SUBMODULE_PATCH_WITHOUT_INDEX;
                } else {
                        if (read_old_data(st, name, buf))
                                return error(_("read of %s failed"), name);
                }
        }
        return 0;
}

/*
 * We are about to apply "patch"; populate the "image" with the
 * current version we have, from the working tree or from the index,
 * depending on the situation e.g. --cached/--index.  If we are
 * applying a non-git patch that incrementally updates the tree,
 * we read from the result of a previous diff.
 */
static int load_preimage(struct image *image,
                         struct patch *patch, struct stat *st,
                         const struct cache_entry *ce)
{
        struct strbuf buf = STRBUF_INIT;
        size_t len;
        char *img;
        struct patch *previous;
        int status;

        previous = previous_patch(patch, &status);
        if (status)
                return error(_("path %s has been renamed/deleted"),
                             patch->old_name);
        if (previous) {
                /* We have a patched copy in memory; use that. */
                strbuf_add(&buf, previous->result, previous->resultsize);
        } else {
                status = load_patch_target(&buf, ce, st,
                                           patch->old_name, patch->old_mode);
                if (status < 0)
                        return status;
                else if (status == SUBMODULE_PATCH_WITHOUT_INDEX) {
                        /*
                         * There is no way to apply subproject
                         * patch without looking at the index.
                         * NEEDSWORK: shouldn't this be flagged
                         * as an error???
                         */
                        free_fragment_list(patch->fragments);
                        patch->fragments = NULL;
                } else if (status) {
                        return error(_("read of %s failed"), patch->old_name);
                }
        }

        img = strbuf_detach(&buf, &len);
        prepare_image(image, img, len, !patch->is_binary);
        return 0;
}

static int three_way_merge(struct image *image,
                           char *path,
                           const unsigned char *base,
                           const unsigned char *ours,
                           const unsigned char *theirs)
{
        mmfile_t base_file, our_file, their_file;
        mmbuffer_t result = { NULL };
        int status;

        read_mmblob(&base_file, base);
        read_mmblob(&our_file, ours);
        read_mmblob(&their_file, theirs);
        status = ll_merge(&result, path,
                          &base_file, "base",
                          &our_file, "ours",
                          &their_file, "theirs", NULL);
        free(base_file.ptr);
        free(our_file.ptr);
        free(their_file.ptr);
        if (status < 0 || !result.ptr) {
                free(result.ptr);
                return -1;
        }
        clear_image(image);
        image->buf = result.ptr;
        image->len = result.size;

        return status;
}

/*
 * When directly falling back to add/add three-way merge, we read from
 * the current contents of the new_name.  In no cases other than that
 * this function will be called.
 */
static int load_current(struct image *image, struct patch *patch)
{
        struct strbuf buf = STRBUF_INIT;
        int status, pos;
        size_t len;
        char *img;
        struct stat st;
        struct cache_entry *ce;
        char *name = patch->new_name;
        unsigned mode = patch->new_mode;

        if (!patch->is_new)
                die("BUG: patch to %s is not a creation", patch->old_name);

        pos = cache_name_pos(name, strlen(name));
        if (pos < 0)
                return error(_("%s: does not exist in index"), name);
        ce = active_cache[pos];
        if (lstat(name, &st)) {
                if (errno != ENOENT)
                        return error(_("%s: %s"), name, strerror(errno));
                if (checkout_target(&the_index, ce, &st))
                        return -1;
        }
        if (verify_index_match(ce, &st))
                return error(_("%s: does not match index"), name);

        status = load_patch_target(&buf, ce, &st, name, mode);
        if (status < 0)
                return status;
        else if (status)
                return -1;
        img = strbuf_detach(&buf, &len);
        prepare_image(image, img, len, !patch->is_binary);
        return 0;
}

static int try_threeway(struct image *image, struct patch *patch,
                        struct stat *st, const struct cache_entry *ce)
{
        unsigned char pre_sha1[20], post_sha1[20], our_sha1[20];
        struct strbuf buf = STRBUF_INIT;
        size_t len;
        int status;
        char *img;
        struct image tmp_image;

        /* No point falling back to 3-way merge in these cases */
        if (patch->is_delete ||
            S_ISGITLINK(patch->old_mode) || S_ISGITLINK(patch->new_mode))
                return -1;

        /* Preimage the patch was prepared for */
        if (patch->is_new)
                write_sha1_file("", 0, blob_type, pre_sha1);
        else if (get_sha1(patch->old_sha1_prefix, pre_sha1) ||
                 read_blob_object(&buf, pre_sha1, patch->old_mode))
                return error("repository lacks the necessary blob to fall back on 3-way merge.");

        fprintf(stderr, "Falling back to three-way merge...\n");

        img = strbuf_detach(&buf, &len);
        prepare_image(&tmp_image, img, len, 1);
        /* Apply the patch to get the post image */
        if (apply_fragments(&tmp_image, patch) < 0) {
                clear_image(&tmp_image);
                return -1;
        }
        /* post_sha1[] is theirs */
        write_sha1_file(tmp_image.buf, tmp_image.len, blob_type, post_sha1);
        clear_image(&tmp_image);

        /* our_sha1[] is ours */
        if (patch->is_new) {
                if (load_current(&tmp_image, patch))
                        return error("cannot read the current contents of '%s'",
                                     patch->new_name);
        } else {
                if (load_preimage(&tmp_image, patch, st, ce))
                        return error("cannot read the current contents of '%s'",
                                     patch->old_name);
        }
        write_sha1_file(tmp_image.buf, tmp_image.len, blob_type, our_sha1);
        clear_image(&tmp_image);

        /* in-core three-way merge between post and our using pre as base */
        status = three_way_merge(image, patch->new_name,
                                 pre_sha1, our_sha1, post_sha1);
        if (status < 0) {
                fprintf(stderr, "Failed to fall back on three-way merge...\n");
                return status;
        }

        if (status) {
                patch->conflicted_threeway = 1;
                if (patch->is_new)
                        hashclr(patch->threeway_stage[0]);
                else
                        hashcpy(patch->threeway_stage[0], pre_sha1);
                hashcpy(patch->threeway_stage[1], our_sha1);
                hashcpy(patch->threeway_stage[2], post_sha1);
                fprintf(stderr, "Applied patch to '%s' with conflicts.\n", patch->new_name);
        } else {
                fprintf(stderr, "Applied patch to '%s' cleanly.\n", patch->new_name);
        }
        return 0;
}

static int apply_data(struct patch *patch, struct stat *st, const struct cache_entry *ce)
{
        struct image image;

        if (load_preimage(&image, patch, st, ce) < 0)
                return -1;

        if (patch->direct_to_threeway ||
            apply_fragments(&image, patch) < 0) {
                /* Note: with --reject, apply_fragments() returns 0 */
                if (!threeway || try_threeway(&image, patch, st, ce) < 0)
                        return -1;
        }
        patch->result = image.buf;
        patch->resultsize = image.len;
        add_to_fn_table(patch);
        free(image.line_allocated);

        if (0 < patch->is_delete && patch->resultsize)
                return error(_("removal patch leaves file contents"));

        return 0;
}

/*
 * If "patch" that we are looking at modifies or deletes what we have,
 * we would want it not to lose any local modification we have, either
 * in the working tree or in the index.
 *
 * This also decides if a non-git patch is a creation patch or a
 * modification to an existing empty file.  We do not check the state
 * of the current tree for a creation patch in this function; the caller
 * check_patch() separately makes sure (and errors out otherwise) that
 * the path the patch creates does not exist in the current tree.
 */
static int check_preimage(struct patch *patch, struct cache_entry **ce, struct stat *st)
{
        const char *old_name = patch->old_name;
        struct patch *previous = NULL;
        int stat_ret = 0, status;
        unsigned st_mode = 0;

        if (!old_name)
                return 0;

        assert(patch->is_new <= 0);
        previous = previous_patch(patch, &status);

        if (status)
                return error(_("path %s has been renamed/deleted"), old_name);
        if (previous) {
                st_mode = previous->new_mode;
        } else if (!cached) {
                stat_ret = lstat(old_name, st);
                if (stat_ret && errno != ENOENT)
                        return error(_("%s: %s"), old_name, strerror(errno));
        }

        if (check_index && !previous) {
                int pos = cache_name_pos(old_name, strlen(old_name));
                if (pos < 0) {
                        if (patch->is_new < 0)
                                goto is_new;
                        return error(_("%s: does not exist in index"), old_name);
                }
                *ce = active_cache[pos];
                if (stat_ret < 0) {
                        if (checkout_target(&the_index, *ce, st))
                                return -1;
                }
                if (!cached && verify_index_match(*ce, st))
                        return error(_("%s: does not match index"), old_name);
                if (cached)
                        st_mode = (*ce)->ce_mode;
        } else if (stat_ret < 0) {
                if (patch->is_new < 0)
                        goto is_new;
                return error(_("%s: %s"), old_name, strerror(errno));
        }

        if (!cached && !previous)
                st_mode = ce_mode_from_stat(*ce, st->st_mode);

        if (patch->is_new < 0)
                patch->is_new = 0;
        if (!patch->old_mode)
                patch->old_mode = st_mode;
        if ((st_mode ^ patch->old_mode) & S_IFMT)
                return error(_("%s: wrong type"), old_name);
        if (st_mode != patch->old_mode)
                warning(_("%s has type %o, expected %o"),
                        old_name, st_mode, patch->old_mode);
        if (!patch->new_mode && !patch->is_delete)
                patch->new_mode = st_mode;
        return 0;

 is_new:
        patch->is_new = 1;
        patch->is_delete = 0;
        free(patch->old_name);
        patch->old_name = NULL;
        return 0;
}


#define EXISTS_IN_INDEX 1
#define EXISTS_IN_WORKTREE 2

static int check_to_create(const char *new_name, int ok_if_exists)
{
        struct stat nst;

        if (check_index &&
            cache_name_pos(new_name, strlen(new_name)) >= 0 &&
            !ok_if_exists)
                return EXISTS_IN_INDEX;
        if (cached)
                return 0;

        if (!lstat(new_name, &nst)) {
                if (S_ISDIR(nst.st_mode) || ok_if_exists)
                        return 0;
                /*
                 * A leading component of new_name might be a symlink
                 * that is going to be removed with this patch, but
                 * still pointing at somewhere that has the path.
                 * In such a case, path "new_name" does not exist as
                 * far as git is concerned.
                 */
                if (has_symlink_leading_path(new_name, strlen(new_name)))
                        return 0;

                return EXISTS_IN_WORKTREE;
        } else if ((errno != ENOENT) && (errno != ENOTDIR)) {
                return error("%s: %s", new_name, strerror(errno));
        }
        return 0;
}

/*
 * Check and apply the patch in-core; leave the result in patch->result
 * for the caller to write it out to the final destination.
 */
static int check_patch(struct patch *patch)
{
        struct stat st;
        const char *old_name = patch->old_name;
        const char *new_name = patch->new_name;
        const char *name = old_name ? old_name : new_name;
        struct cache_entry *ce = NULL;
        struct patch *tpatch;
        int ok_if_exists;
        int status;

        patch->rejected = 1; /* we will drop this after we succeed */

        status = check_preimage(patch, &ce, &st);
        if (status)
                return status;
        old_name = patch->old_name;

        /*
         * A type-change diff is always split into a patch to delete
         * old, immediately followed by a patch to create new (see
         * diff.c::run_diff()); in such a case it is Ok that the entry
         * to be deleted by the previous patch is still in the working
         * tree and in the index.
         *
         * A patch to swap-rename between A and B would first rename A
         * to B and then rename B to A.  While applying the first one,
         * the presence of B should not stop A from getting renamed to
         * B; ask to_be_deleted() about the later rename.  Removal of
         * B and rename from A to B is handled the same way by asking
         * was_deleted().
         */
        if ((tpatch = in_fn_table(new_name)) &&
            (was_deleted(tpatch) || to_be_deleted(tpatch)))
                ok_if_exists = 1;
        else
                ok_if_exists = 0;

        if (new_name &&
            ((0 < patch->is_new) || patch->is_rename || patch->is_copy)) {
                int err = check_to_create(new_name, ok_if_exists);

                if (err && threeway) {
                        patch->direct_to_threeway = 1;
                } else switch (err) {
                case 0:
                        break; /* happy */
                case EXISTS_IN_INDEX:
                        return error(_("%s: already exists in index"), new_name);
                        break;
                case EXISTS_IN_WORKTREE:
                        return error(_("%s: already exists in working directory"),
                                     new_name);
                default:
                        return err;
                }

                if (!patch->new_mode) {
                        if (0 < patch->is_new)
                                patch->new_mode = S_IFREG | 0644;
                        else
                                patch->new_mode = patch->old_mode;
                }
        }

        if (new_name && old_name) {
                int same = !strcmp(old_name, new_name);
                if (!patch->new_mode)
                        patch->new_mode = patch->old_mode;
                if ((patch->old_mode ^ patch->new_mode) & S_IFMT) {
                        if (same)
                                return error(_("new mode (%o) of %s does not "
                                               "match old mode (%o)"),
                                        patch->new_mode, new_name,
                                        patch->old_mode);
                        else
                                return error(_("new mode (%o) of %s does not "
                                               "match old mode (%o) of %s"),
                                        patch->new_mode, new_name,
                                        patch->old_mode, old_name);
                }
        }

        if (apply_data(patch, &st, ce) < 0)
                return error(_("%s: patch does not apply"), name);
        patch->rejected = 0;
        return 0;
}

static int check_patch_list(struct patch *patch)
{
        int err = 0;

        prepare_fn_table(patch);
        while (patch) {
                if (apply_verbosely)
                        say_patch_name(stderr,
                                       _("Checking patch %s..."), patch);
                err |= check_patch(patch);
                patch = patch->next;
        }
        return err;
}

/* This function tries to read the sha1 from the current index */
static int get_current_sha1(const char *path, unsigned char *sha1)
{
        int pos;

        if (read_cache() < 0)
                return -1;
        pos = cache_name_pos(path, strlen(path));
        if (pos < 0)
                return -1;
        hashcpy(sha1, active_cache[pos]->sha1);
        return 0;
}

static int preimage_sha1_in_gitlink_patch(struct patch *p, unsigned char sha1[20])
{
        /*
         * A usable gitlink patch has only one fragment (hunk) that looks like:
         * @@ -1 +1 @@
         * -Subproject commit <old sha1>
         * +Subproject commit <new sha1>
         * or
         * @@ -1 +0,0 @@
         * -Subproject commit <old sha1>
         * for a removal patch.
         */
        struct fragment *hunk = p->fragments;
        static const char heading[] = "-Subproject commit ";
        char *preimage;

        if (/* does the patch have only one hunk? */
            hunk && !hunk->next &&
            /* is its preimage one line? */
            hunk->oldpos == 1 && hunk->oldlines == 1 &&
            /* does preimage begin with the heading? */
            (preimage = memchr(hunk->patch, '\n', hunk->size)) != NULL &&
            starts_with(++preimage, heading) &&
            /* does it record full SHA-1? */
            !get_sha1_hex(preimage + sizeof(heading) - 1, sha1) &&
            preimage[sizeof(heading) + 40 - 1] == '\n' &&
            /* does the abbreviated name on the index line agree with it? */
            starts_with(preimage + sizeof(heading) - 1, p->old_sha1_prefix))
                return 0; /* it all looks fine */

        /* we may have full object name on the index line */
        return get_sha1_hex(p->old_sha1_prefix, sha1);
}

/* Build an index that contains the just the files needed for a 3way merge */
static void build_fake_ancestor(struct patch *list, const char *filename)
{
        struct patch *patch;
        struct index_state result = { NULL };
        static struct lock_file lock;

        /* Once we start supporting the reverse patch, it may be
         * worth showing the new sha1 prefix, but until then...
         */
        for (patch = list; patch; patch = patch->next) {
                unsigned char sha1[20];
                struct cache_entry *ce;
                const char *name;

                name = patch->old_name ? patch->old_name : patch->new_name;
                if (0 < patch->is_new)
                        continue;

                if (S_ISGITLINK(patch->old_mode)) {
                        if (!preimage_sha1_in_gitlink_patch(patch, sha1))
                                ; /* ok, the textual part looks sane */
                        else
                                die("sha1 information is lacking or useless for submoule %s",
                                    name);
                } else if (!get_sha1_blob(patch->old_sha1_prefix, sha1)) {
                        ; /* ok */
                } else if (!patch->lines_added && !patch->lines_deleted) {
                        /* mode-only change: update the current */
                        if (get_current_sha1(patch->old_name, sha1))
                                die("mode change for %s, which is not "
                                    "in current HEAD", name);
                } else
                        die("sha1 information is lacking or useless "
                            "(%s).", name);

                ce = make_cache_entry(patch->old_mode, sha1, name, 0, 0);
                if (!ce)
                        die(_("make_cache_entry failed for path '%s'"), name);
                if (add_index_entry(&result, ce, ADD_CACHE_OK_TO_ADD))
                        die ("Could not add %s to temporary index", name);
        }

        hold_lock_file_for_update(&lock, filename, LOCK_DIE_ON_ERROR);
        if (write_locked_index(&result, &lock, COMMIT_LOCK))
                die ("Could not write temporary index to %s", filename);

        discard_index(&result);
}

static void stat_patch_list(struct patch *patch)
{
        int files, adds, dels;

        for (files = adds = dels = 0 ; patch ; patch = patch->next) {
                files++;
                adds += patch->lines_added;
                dels += patch->lines_deleted;
                show_stats(patch);
        }

        print_stat_summary(stdout, files, adds, dels);
}

static void numstat_patch_list(struct patch *patch)
{
        for ( ; patch; patch = patch->next) {
                const char *name;
                name = patch->new_name ? patch->new_name : patch->old_name;
                if (patch->is_binary)
                        printf("-\t-\t");
                else
                        printf("%d\t%d\t", patch->lines_added, patch->lines_deleted);
                write_name_quoted(name, stdout, line_termination);
        }
}

static void show_file_mode_name(const char *newdelete, unsigned int mode, const char *name)
{
        if (mode)
                printf(" %s mode %06o %s\n", newdelete, mode, name);
        else
                printf(" %s %s\n", newdelete, name);
}

static void show_mode_change(struct patch *p, int show_name)
{
        if (p->old_mode && p->new_mode && p->old_mode != p->new_mode) {
                if (show_name)
                        printf(" mode change %06o => %06o %s\n",
                               p->old_mode, p->new_mode, p->new_name);
                else
                        printf(" mode change %06o => %06o\n",
                               p->old_mode, p->new_mode);
        }
}

static void show_rename_copy(struct patch *p)
{
        const char *renamecopy = p->is_rename ? "rename" : "copy";
        const char *old, *new;

        /* Find common prefix */
        old = p->old_name;
        new = p->new_name;
        while (1) {
                const char *slash_old, *slash_new;
                slash_old = strchr(old, '/');
                slash_new = strchr(new, '/');
                if (!slash_old ||
                    !slash_new ||
                    slash_old - old != slash_new - new ||
                    memcmp(old, new, slash_new - new))
                        break;
                old = slash_old + 1;
                new = slash_new + 1;
        }
        /* p->old_name thru old is the common prefix, and old and new
         * through the end of names are renames
         */
        if (old != p->old_name)
                printf(" %s %.*s{%s => %s} (%d%%)\n", renamecopy,
                       (int)(old - p->old_name), p->old_name,
                       old, new, p->score);
        else
                printf(" %s %s => %s (%d%%)\n", renamecopy,
                       p->old_name, p->new_name, p->score);
        show_mode_change(p, 0);
}

static void summary_patch_list(struct patch *patch)
{
        struct patch *p;

        for (p = patch; p; p = p->next) {
                if (p->is_new)
                        show_file_mode_name("create", p->new_mode, p->new_name);
                else if (p->is_delete)
                        show_file_mode_name("delete", p->old_mode, p->old_name);
                else {
                        if (p->is_rename || p->is_copy)
                                show_rename_copy(p);
                        else {
                                if (p->score) {
                                        printf(" rewrite %s (%d%%)\n",
                                               p->new_name, p->score);
                                        show_mode_change(p, 0);
                                }
                                else
                                        show_mode_change(p, 1);
                        }
                }
        }
}

static void patch_stats(struct patch *patch)
{
        int lines = patch->lines_added + patch->lines_deleted;

        if (lines > max_change)
                max_change = lines;
        if (patch->old_name) {
                int len = quote_c_style(patch->old_name, NULL, NULL, 0);
                if (!len)
                        len = strlen(patch->old_name);
                if (len > max_len)
                        max_len = len;
        }
        if (patch->new_name) {
                int len = quote_c_style(patch->new_name, NULL, NULL, 0);
                if (!len)
                        len = strlen(patch->new_name);
                if (len > max_len)
                        max_len = len;
        }
}

static void remove_file(struct patch *patch, int rmdir_empty)
{
        if (update_index) {
                if (remove_file_from_cache(patch->old_name) < 0)
                        die(_("unable to remove %s from index"), patch->old_name);
        }
        if (!cached) {
                if (!remove_or_warn(patch->old_mode, patch->old_name) && rmdir_empty) {
                        remove_path(patch->old_name);
                }
        }
}

static void add_index_file(const char *path, unsigned mode, void *buf, unsigned long size)
{
        struct stat st;
        struct cache_entry *ce;
        int namelen = strlen(path);
        unsigned ce_size = cache_entry_size(namelen);

        if (!update_index)
                return;

        ce = xcalloc(1, ce_size);
        memcpy(ce->name, path, namelen);
        ce->ce_mode = create_ce_mode(mode);
        ce->ce_flags = create_ce_flags(0);
        ce->ce_namelen = namelen;
        if (S_ISGITLINK(mode)) {
                const char *s;

                if (!skip_prefix(buf, "Subproject commit ", &s) ||
                    get_sha1_hex(s, ce->sha1))
                        die(_("corrupt patch for submodule %s"), path);
        } else {
                if (!cached) {
                        if (lstat(path, &st) < 0)
                                die_errno(_("unable to stat newly created file '%s'"),
                                          path);
                        fill_stat_cache_info(ce, &st);
                }
                if (write_sha1_file(buf, size, blob_type, ce->sha1) < 0)
                        die(_("unable to create backing store for newly created file %s"), path);
        }
        if (add_cache_entry(ce, ADD_CACHE_OK_TO_ADD) < 0)
                die(_("unable to add cache entry for %s"), path);
}

static int try_create_file(const char *path, unsigned int mode, const char *buf, unsigned long size)
{
        int fd;
        struct strbuf nbuf = STRBUF_INIT;

        if (S_ISGITLINK(mode)) {
                struct stat st;
                if (!lstat(path, &st) && S_ISDIR(st.st_mode))
                        return 0;
                return mkdir(path, 0777);
        }

        if (has_symlinks && S_ISLNK(mode))
                /* Although buf:size is counted string, it also is NUL
                 * terminated.
                 */
                return symlink(buf, path);

        fd = open(path, O_CREAT | O_EXCL | O_WRONLY, (mode & 0100) ? 0777 : 0666);
        if (fd < 0)
                return -1;

        if (convert_to_working_tree(path, buf, size, &nbuf)) {
                size = nbuf.len;
                buf  = nbuf.buf;
        }
        write_or_die(fd, buf, size);
        strbuf_release(&nbuf);

        if (close(fd) < 0)
                die_errno(_("closing file '%s'"), path);
        return 0;
}

/*
 * We optimistically assume that the directories exist,
 * which is true 99% of the time anyway. If they don't,
 * we create them and try again.
 */
static void create_one_file(char *path, unsigned mode, const char *buf, unsigned long size)
{
        if (cached)
                return;
        if (!try_create_file(path, mode, buf, size))
                return;

        if (errno == ENOENT) {
                if (safe_create_leading_directories(path))
                        return;
                if (!try_create_file(path, mode, buf, size))
                        return;
        }

        if (errno == EEXIST || errno == EACCES) {
                /* We may be trying to create a file where a directory
                 * used to be.
                 */
                struct stat st;
                if (!lstat(path, &st) && (!S_ISDIR(st.st_mode) || !rmdir(path)))
                        errno = EEXIST;
        }

        if (errno == EEXIST) {
                unsigned int nr = getpid();

                for (;;) {
                        char newpath[PATH_MAX];
                        mksnpath(newpath, sizeof(newpath), "%s~%u", path, nr);
                        if (!try_create_file(newpath, mode, buf, size)) {
                                if (!rename(newpath, path))
                                        return;
                                unlink_or_warn(newpath);
                                break;
                        }
                        if (errno != EEXIST)
                                break;
                        ++nr;
                }
        }
        die_errno(_("unable to write file '%s' mode %o"), path, mode);
}

static void add_conflicted_stages_file(struct patch *patch)
{
        int stage, namelen;
        unsigned ce_size, mode;
        struct cache_entry *ce;

        if (!update_index)
                return;
        namelen = strlen(patch->new_name);
        ce_size = cache_entry_size(namelen);
        mode = patch->new_mode ? patch->new_mode : (S_IFREG | 0644);

        remove_file_from_cache(patch->new_name);
        for (stage = 1; stage < 4; stage++) {
                if (is_null_sha1(patch->threeway_stage[stage - 1]))
                        continue;
                ce = xcalloc(1, ce_size);
                memcpy(ce->name, patch->new_name, namelen);
                ce->ce_mode = create_ce_mode(mode);
                ce->ce_flags = create_ce_flags(stage);
                ce->ce_namelen = namelen;
                hashcpy(ce->sha1, patch->threeway_stage[stage - 1]);
                if (add_cache_entry(ce, ADD_CACHE_OK_TO_ADD) < 0)
                        die(_("unable to add cache entry for %s"), patch->new_name);
        }
}

static void create_file(struct patch *patch)
{
        char *path = patch->new_name;
        unsigned mode = patch->new_mode;
        unsigned long size = patch->resultsize;
        char *buf = patch->result;

        if (!mode)
                mode = S_IFREG | 0644;
        create_one_file(path, mode, buf, size);

        if (patch->conflicted_threeway)
                add_conflicted_stages_file(patch);
        else
                add_index_file(path, mode, buf, size);
}

/* phase zero is to remove, phase one is to create */
static void write_out_one_result(struct patch *patch, int phase)
{
        if (patch->is_delete > 0) {
                if (phase == 0)
                        remove_file(patch, 1);
                return;
        }
        if (patch->is_new > 0 || patch->is_copy) {
                if (phase == 1)
                        create_file(patch);
                return;
        }
        /*
         * Rename or modification boils down to the same
         * thing: remove the old, write the new
         */
        if (phase == 0)
                remove_file(patch, patch->is_rename);
        if (phase == 1)
                create_file(patch);
}

static int write_out_one_reject(struct patch *patch)
{
        FILE *rej;
        char namebuf[PATH_MAX];
        struct fragment *frag;
        int cnt = 0;
        struct strbuf sb = STRBUF_INIT;

        for (cnt = 0, frag = patch->fragments; frag; frag = frag->next) {
                if (!frag->rejected)
                        continue;
                cnt++;
        }

        if (!cnt) {
                if (apply_verbosely)
                        say_patch_name(stderr,
                                       _("Applied patch %s cleanly."), patch);
                return 0;
        }

        /* This should not happen, because a removal patch that leaves
         * contents are marked "rejected" at the patch level.
         */
        if (!patch->new_name)
                die(_("internal error"));

        /* Say this even without --verbose */
        strbuf_addf(&sb, Q_("Applying patch %%s with %d reject...",
                            "Applying patch %%s with %d rejects...",
                            cnt),
                    cnt);
        say_patch_name(stderr, sb.buf, patch);
        strbuf_release(&sb);

        cnt = strlen(patch->new_name);
        if (ARRAY_SIZE(namebuf) <= cnt + 5) {
                cnt = ARRAY_SIZE(namebuf) - 5;
                warning(_("truncating .rej filename to %.*s.rej"),
                        cnt - 1, patch->new_name);
        }
        memcpy(namebuf, patch->new_name, cnt);
        memcpy(namebuf + cnt, ".rej", 5);

        rej = fopen(namebuf, "w");
        if (!rej)
                return error(_("cannot open %s: %s"), namebuf, strerror(errno));

        /* Normal git tools never deal with .rej, so do not pretend
         * this is a git patch by saying --git or giving extended
         * headers.  While at it, maybe please "kompare" that wants
         * the trailing TAB and some garbage at the end of line ;-).
         */
        fprintf(rej, "diff a/%s b/%s\t(rejected hunks)\n",
                patch->new_name, patch->new_name);
        for (cnt = 1, frag = patch->fragments;
             frag;
             cnt++, frag = frag->next) {
                if (!frag->rejected) {
                        fprintf_ln(stderr, _("Hunk #%d applied cleanly."), cnt);
                        continue;
                }
                fprintf_ln(stderr, _("Rejected hunk #%d."), cnt);
                fprintf(rej, "%.*s", frag->size, frag->patch);
                if (frag->patch[frag->size-1] != '\n')
                        fputc('\n', rej);
        }
        fclose(rej);
        return -1;
}

static int write_out_results(struct patch *list)
{
        int phase;
        int errs = 0;
        struct patch *l;
        struct string_list cpath = STRING_LIST_INIT_DUP;

        for (phase = 0; phase < 2; phase++) {
                l = list;
                while (l) {
                        if (l->rejected)
                                errs = 1;
                        else {
                                write_out_one_result(l, phase);
                                if (phase == 1) {
                                        if (write_out_one_reject(l))
                                                errs = 1;
                                        if (l->conflicted_threeway) {
                                                string_list_append(&cpath, l->new_name);
                                                errs = 1;
                                        }
                                }
                        }
                        l = l->next;
                }
        }

        if (cpath.nr) {
                struct string_list_item *item;

                sort_string_list(&cpath);
                for_each_string_list_item(item, &cpath)
                        fprintf(stderr, "U %s\n", item->string);
                string_list_clear(&cpath, 0);

                rerere(0);
        }

        return errs;
}

static struct lock_file lock_file;

#define INACCURATE_EOF  (1<<0)
#define RECOUNT         (1<<1)

static int apply_patch(int fd, const char *filename, int options)
{
        size_t offset;
        struct strbuf buf = STRBUF_INIT; /* owns the patch text */
        struct patch *list = NULL, **listp = &list;
        int skipped_patch = 0;

        patch_input_file = filename;
        read_patch_file(&buf, fd);
        offset = 0;
        while (offset < buf.len) {
                struct patch *patch;
                int nr;

                patch = xcalloc(1, sizeof(*patch));
                patch->inaccurate_eof = !!(options & INACCURATE_EOF);
                patch->recount =  !!(options & RECOUNT);
                nr = parse_chunk(buf.buf + offset, buf.len - offset, patch);
                if (nr < 0)
                        break;
                if (apply_in_reverse)
                        reverse_patches(patch);
                if (use_patch(patch)) {
                        patch_stats(patch);
                        *listp = patch;
                        listp = &patch->next;
                }
                else {
                        free_patch(patch);
                        skipped_patch++;
                }
                offset += nr;
        }

        if (!list && !skipped_patch)
                die(_("unrecognized input"));

        if (whitespace_error && (ws_error_action == die_on_ws_error))
                apply = 0;

        update_index = check_index && apply;
        if (update_index && newfd < 0)
                newfd = hold_locked_index(&lock_file, 1);

        if (check_index) {
                if (read_cache() < 0)
                        die(_("unable to read index file"));
        }

        if ((check || apply) &&
            check_patch_list(list) < 0 &&
            !apply_with_reject)
                exit(1);

        if (apply && write_out_results(list)) {
                if (apply_with_reject)
                        exit(1);
                /* with --3way, we still need to write the index out */
                return 1;
        }

        if (fake_ancestor)
                build_fake_ancestor(list, fake_ancestor);

        if (diffstat)
                stat_patch_list(list);

        if (numstat)
                numstat_patch_list(list);

        if (summary)
                summary_patch_list(list);

        free_patch_list(list);
        strbuf_release(&buf);
        string_list_clear(&fn_table, 0);
        return 0;
}

static void git_apply_config(void)
{
        git_config_get_string_const("apply.whitespace", &apply_default_whitespace);
        git_config_get_string_const("apply.ignorewhitespace", &apply_default_ignorewhitespace);
        git_config(git_default_config, NULL);
}

static int option_parse_exclude(const struct option *opt,
                                const char *arg, int unset)
{
        add_name_limit(arg, 1);
        return 0;
}

static int option_parse_include(const struct option *opt,
                                const char *arg, int unset)
{
        add_name_limit(arg, 0);
        has_include = 1;
        return 0;
}

static int option_parse_p(const struct option *opt,
                          const char *arg, int unset)
{
        p_value = atoi(arg);
        p_value_known = 1;
        return 0;
}

static int option_parse_z(const struct option *opt,
                          const char *arg, int unset)
{
        if (unset)
                line_termination = '\n';
        else
                line_termination = 0;
        return 0;
}

static int option_parse_space_change(const struct option *opt,
                          const char *arg, int unset)
{
        if (unset)
                ws_ignore_action = ignore_ws_none;
        else
                ws_ignore_action = ignore_ws_change;
        return 0;
}

static int option_parse_whitespace(const struct option *opt,
                                   const char *arg, int unset)
{
        const char **whitespace_option = opt->value;

        *whitespace_option = arg;
        parse_whitespace_option(arg);
        return 0;
}

static int option_parse_directory(const struct option *opt,
                                  const char *arg, int unset)
{
        root_len = strlen(arg);
        if (root_len && arg[root_len - 1] != '/') {
                char *new_root;
                root = new_root = xmalloc(root_len + 2);
                strcpy(new_root, arg);
                strcpy(new_root + root_len++, "/");
        } else
                root = arg;
        return 0;
}

int cmd_apply(int argc, const char **argv, const char *prefix_)
{
        int i;
        int errs = 0;
        int is_not_gitdir = !startup_info->have_repository;
        int force_apply = 0;

        const char *whitespace_option = NULL;

        struct option builtin_apply_options[] = {
                { OPTION_CALLBACK, 0, "exclude", NULL, N_("path"),
                        N_("don't apply changes matching the given path"),
                        0, option_parse_exclude },
                { OPTION_CALLBACK, 0, "include", NULL, N_("path"),
                        N_("apply changes matching the given path"),
                        0, option_parse_include },
                { OPTION_CALLBACK, 'p', NULL, NULL, N_("num"),
                        N_("remove <num> leading slashes from traditional diff paths"),
                        0, option_parse_p },
                OPT_BOOL(0, "no-add", &no_add,
                        N_("ignore additions made by the patch")),
                OPT_BOOL(0, "stat", &diffstat,
                        N_("instead of applying the patch, output diffstat for the input")),
                OPT_NOOP_NOARG(0, "allow-binary-replacement"),
                OPT_NOOP_NOARG(0, "binary"),
                OPT_BOOL(0, "numstat", &numstat,
                        N_("show number of added and deleted lines in decimal notation")),
                OPT_BOOL(0, "summary", &summary,
                        N_("instead of applying the patch, output a summary for the input")),
                OPT_BOOL(0, "check", &check,
                        N_("instead of applying the patch, see if the patch is applicable")),
                OPT_BOOL(0, "index", &check_index,
                        N_("make sure the patch is applicable to the current index")),
                OPT_BOOL(0, "cached", &cached,
                        N_("apply a patch without touching the working tree")),
                OPT_BOOL(0, "apply", &force_apply,
                        N_("also apply the patch (use with --stat/--summary/--check)")),
                OPT_BOOL('3', "3way", &threeway,
                         N_( "attempt three-way merge if a patch does not apply")),
                OPT_FILENAME(0, "build-fake-ancestor", &fake_ancestor,
                        N_("build a temporary index based on embedded index information")),
                { OPTION_CALLBACK, 'z', NULL, NULL, NULL,
                        N_("paths are separated with NUL character"),
                        PARSE_OPT_NOARG, option_parse_z },
                OPT_INTEGER('C', NULL, &p_context,
                                N_("ensure at least <n> lines of context match")),
                { OPTION_CALLBACK, 0, "whitespace", &whitespace_option, N_("action"),
                        N_("detect new or modified lines that have whitespace errors"),
                        0, option_parse_whitespace },
                { OPTION_CALLBACK, 0, "ignore-space-change", NULL, NULL,
                        N_("ignore changes in whitespace when finding context"),
                        PARSE_OPT_NOARG, option_parse_space_change },
                { OPTION_CALLBACK, 0, "ignore-whitespace", NULL, NULL,
                        N_("ignore changes in whitespace when finding context"),
                        PARSE_OPT_NOARG, option_parse_space_change },
                OPT_BOOL('R', "reverse", &apply_in_reverse,
                        N_("apply the patch in reverse")),
                OPT_BOOL(0, "unidiff-zero", &unidiff_zero,
                        N_("don't expect at least one line of context")),
                OPT_BOOL(0, "reject", &apply_with_reject,
                        N_("leave the rejected hunks in corresponding *.rej files")),
                OPT_BOOL(0, "allow-overlap", &allow_overlap,
                        N_("allow overlapping hunks")),
                OPT__VERBOSE(&apply_verbosely, N_("be verbose")),
                OPT_BIT(0, "inaccurate-eof", &options,
                        N_("tolerate incorrectly detected missing new-line at the end of file"),
                        INACCURATE_EOF),
                OPT_BIT(0, "recount", &options,
                        N_("do not trust the line counts in the hunk headers"),
                        RECOUNT),
                { OPTION_CALLBACK, 0, "directory", NULL, N_("root"),
                        N_("prepend <root> to all filenames"),
                        0, option_parse_directory },
                OPT_END()
        };

        prefix = prefix_;
        prefix_length = prefix ? strlen(prefix) : 0;
        git_apply_config();
        if (apply_default_whitespace)
                parse_whitespace_option(apply_default_whitespace);
        if (apply_default_ignorewhitespace)
                parse_ignorewhitespace_option(apply_default_ignorewhitespace);

        argc = parse_options(argc, argv, prefix, builtin_apply_options,
                        apply_usage, 0);

        if (apply_with_reject && threeway)
                die("--reject and --3way cannot be used together.");
        if (cached && threeway)
                die("--cached and --3way cannot be used together.");
        if (threeway) {
                if (is_not_gitdir)
                        die(_("--3way outside a repository"));
                check_index = 1;
        }
        if (apply_with_reject)
                apply = apply_verbosely = 1;
        if (!force_apply && (diffstat || numstat || summary || check || fake_ancestor))
                apply = 0;
        if (check_index && is_not_gitdir)
                die(_("--index outside a repository"));
        if (cached) {
                if (is_not_gitdir)
                        die(_("--cached outside a repository"));
                check_index = 1;
        }
        for (i = 0; i < argc; i++) {
                const char *arg = argv[i];
                int fd;

                if (!strcmp(arg, "-")) {
                        errs |= apply_patch(0, "<stdin>", options);
                        read_stdin = 0;
                        continue;
                } else if (0 < prefix_length)
                        arg = prefix_filename(prefix, prefix_length, arg);

                fd = open(arg, O_RDONLY);
                if (fd < 0)
                        die_errno(_("can't open patch '%s'"), arg);
                read_stdin = 0;
                set_default_whitespace_mode(whitespace_option);
                errs |= apply_patch(fd, arg, options);
                close(fd);
        }
        set_default_whitespace_mode(whitespace_option);
        if (read_stdin)
                errs |= apply_patch(0, "<stdin>", options);
        if (whitespace_error) {
                if (squelch_whitespace_errors &&
                    squelch_whitespace_errors < whitespace_error) {
                        int squelched =
                                whitespace_error - squelch_whitespace_errors;
                        warning(Q_("squelched %d whitespace error",
                                   "squelched %d whitespace errors",
                                   squelched),
                                squelched);
                }
                if (ws_error_action == die_on_ws_error)
                        die(Q_("%d line adds whitespace errors.",
                               "%d lines add whitespace errors.",
                               whitespace_error),
                            whitespace_error);
                if (applied_after_fixing_ws && apply)
                        warning("%d line%s applied after"
                                " fixing whitespace errors.",
                                applied_after_fixing_ws,
                                applied_after_fixing_ws == 1 ? "" : "s");
                else if (whitespace_error)
                        warning(Q_("%d line adds whitespace errors.",
                                   "%d lines add whitespace errors.",
                                   whitespace_error),
                                whitespace_error);
        }

        if (update_index) {
                if (write_locked_index(&the_index, &lock_file, COMMIT_LOCK))
                        die(_("Unable to write new index file"));
        }

        return !!errs;
}