/*
 * Copyright (C) 2005 Junio C Hamano
 */
#include <sys/types.h>
#include <sys/wait.h>
#include <signal.h>
#include "cache.h"
#include "quote.h"
#include "diff.h"
#include "diffcore.h"
#include "xdiff-interface.h"

static int use_size_cache;

int diff_rename_limit_default = -1;

int git_diff_config(const char *var, const char *value)
{
        if (!strcmp(var, "diff.renamelimit")) {
                diff_rename_limit_default = git_config_int(var, value);
                return 0;
        }

        return git_default_config(var, value);
}

static char *quote_one(const char *str)
{
        int needlen;
        char *xp;

        if (!str)
                return NULL;
        needlen = quote_c_style(str, NULL, NULL, 0);
        if (!needlen)
                return strdup(str);
        xp = xmalloc(needlen + 1);
        quote_c_style(str, xp, NULL, 0);
        return xp;
}

static char *quote_two(const char *one, const char *two)
{
        int need_one = quote_c_style(one, NULL, NULL, 1);
        int need_two = quote_c_style(two, NULL, NULL, 1);
        char *xp;

        if (need_one + need_two) {
                if (!need_one) need_one = strlen(one);
                if (!need_two) need_one = strlen(two);

                xp = xmalloc(need_one + need_two + 3);
                xp[0] = '"';
                quote_c_style(one, xp + 1, NULL, 1);
                quote_c_style(two, xp + need_one + 1, NULL, 1);
                strcpy(xp + need_one + need_two + 1, "\"");
                return xp;
        }
        need_one = strlen(one);
        need_two = strlen(two);
        xp = xmalloc(need_one + need_two + 1);
        strcpy(xp, one);
        strcpy(xp + need_one, two);
        return xp;
}

static const char *external_diff(void)
{
        static const char *external_diff_cmd = NULL;
        static int done_preparing = 0;

        if (done_preparing)
                return external_diff_cmd;
        external_diff_cmd = getenv("GIT_EXTERNAL_DIFF");
        done_preparing = 1;
        return external_diff_cmd;
}

#define TEMPFILE_PATH_LEN               50

static struct diff_tempfile {
        const char *name; /* filename external diff should read from */
        char hex[41];
        char mode[10];
        char tmp_path[TEMPFILE_PATH_LEN];
} diff_temp[2];

static int count_lines(const char *data, int size)
{
        int count, ch, completely_empty = 1, nl_just_seen = 0;
        count = 0;
        while (0 < size--) {
                ch = *data++;
                if (ch == '\n') {
                        count++;
                        nl_just_seen = 1;
                        completely_empty = 0;
                }
                else {
                        nl_just_seen = 0;
                        completely_empty = 0;
                }
        }
        if (completely_empty)
                return 0;
        if (!nl_just_seen)
                count++; /* no trailing newline */
        return count;
}

static void print_line_count(int count)
{
        switch (count) {
        case 0:
                printf("0,0");
                break;
        case 1:
                printf("1");
                break;
        default:
                printf("1,%d", count);
                break;
        }
}

static void copy_file(int prefix, const char *data, int size)
{
        int ch, nl_just_seen = 1;
        while (0 < size--) {
                ch = *data++;
                if (nl_just_seen)
                        putchar(prefix);
                putchar(ch);
                if (ch == '\n')
                        nl_just_seen = 1;
                else
                        nl_just_seen = 0;
        }
        if (!nl_just_seen)
                printf("\n\\ No newline at end of file\n");
}

static void emit_rewrite_diff(const char *name_a,
                              const char *name_b,
                              struct diff_filespec *one,
                              struct diff_filespec *two)
{
        int lc_a, lc_b;
        diff_populate_filespec(one, 0);
        diff_populate_filespec(two, 0);
        lc_a = count_lines(one->data, one->size);
        lc_b = count_lines(two->data, two->size);
        printf("--- %s\n+++ %s\n@@ -", name_a, name_b);
        print_line_count(lc_a);
        printf(" +");
        print_line_count(lc_b);
        printf(" @@\n");
        if (lc_a)
                copy_file('-', one->data, one->size);
        if (lc_b)
                copy_file('+', two->data, two->size);
}

static int fill_mmfile(mmfile_t *mf, struct diff_filespec *one)
{
        if (!DIFF_FILE_VALID(one)) {
                mf->ptr = ""; /* does not matter */
                mf->size = 0;
                return 0;
        }
        else if (diff_populate_filespec(one, 0))
                return -1;
        mf->ptr = one->data;
        mf->size = one->size;
        return 0;
}

struct emit_callback {
        const char **label_path;
};

static int fn_out(void *priv, mmbuffer_t *mb, int nbuf)
{
        int i;
        struct emit_callback *ecbdata = priv;

        if (ecbdata->label_path[0]) {
                printf("--- %s\n", ecbdata->label_path[0]);
                printf("+++ %s\n", ecbdata->label_path[1]);
                ecbdata->label_path[0] = ecbdata->label_path[1] = NULL;
        }
        for (i = 0; i < nbuf; i++)
                if (!fwrite(mb[i].ptr, mb[i].size, 1, stdout))
                        return -1;
        return 0;
}

struct diffstat_t {
        struct xdiff_emit_state xm;

        int nr;
        int alloc;
        struct diffstat_file {
                char *name;
                unsigned int added, deleted;
        } **files;
};

static struct diffstat_file *diffstat_add(struct diffstat_t *diffstat,
                const char *name)
{
        struct diffstat_file *x;
        x = xcalloc(sizeof (*x), 1);
        if (diffstat->nr == diffstat->alloc) {
                diffstat->alloc = alloc_nr(diffstat->alloc);
                diffstat->files = xrealloc(diffstat->files,
                                diffstat->alloc * sizeof(x));
        }
        diffstat->files[diffstat->nr++] = x;
        x->name = strdup(name);
        return x;
}

static void diffstat_consume(void *priv, char *line, unsigned long len)
{
        struct diffstat_t *diffstat = priv;
        struct diffstat_file *x = diffstat->files[diffstat->nr - 1];

        if (line[0] == '+')
                x->added++;
        else if (line[0] == '-')
                x->deleted++;
}

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

static void show_stats(struct diffstat_t* data)
{
        char *prefix = "";
        int i, len, add, del, total, adds = 0, dels = 0;
        int max, max_change = 0, max_len = 0;
        int total_files = data->nr;

        if (data->nr == 0)
                return;

        printf("---\n");

        for (i = 0; i < data->nr; i++) {
                struct diffstat_file *file = data->files[i];

                if (max_change < file->added + file->deleted)
                        max_change = file->added + file->deleted;
                len = strlen(file->name);
                if (max_len < len)
                        max_len = len;
        }

        for (i = 0; i < data->nr; i++) {
                char *name = data->files[i]->name;
                int added = data->files[i]->added;
                int deleted = data->files[i]->deleted;

                if (0 < (len = quote_c_style(name, NULL, NULL, 0))) {
                        char *qname = xmalloc(len + 1);
                        quote_c_style(name, qname, NULL, 0);
                        free(name);
                        data->files[i]->name = name = qname;
                }

                /*
                 * "scale" the filename
                 */
                len = strlen(name);
                max = max_len;
                if (max > 50)
                        max = 50;
                if (len > max) {
                        char *slash;
                        prefix = "...";
                        max -= 3;
                        name += len - max;
                        slash = strchr(name, '/');
                        if (slash)
                                name = slash;
                }
                len = max;

                /*
                 * scale the add/delete
                 */
                max = max_change;
                if (max + len > 70)
                        max = 70 - len;

                if (added < 0) {
                        /* binary file */
                        printf(" %s%-*s |  Bin\n", prefix, len, name);
                        goto free_diffstat_file;
                } else if (added + deleted == 0) {
                        total_files--;
                        goto free_diffstat_file;
                }

                add = added;
                del = deleted;
                total = add + del;
                adds += add;
                dels += del;

                if (max_change > 0) {
                        total = (total * max + max_change / 2) / max_change;
                        add = (add * max + max_change / 2) / max_change;
                        del = total - add;
                }
                printf(" %s%-*s |%5d %.*s%.*s\n", prefix,
                                len, name, added + deleted,
                                add, pluses, del, minuses);
        free_diffstat_file:
                free(data->files[i]->name);
                free(data->files[i]);
        }
        free(data->files);
        printf(" %d files changed, %d insertions(+), %d deletions(-)\n",
                        total_files, adds, dels);
}

#define FIRST_FEW_BYTES 8000
static int mmfile_is_binary(mmfile_t *mf)
{
        long sz = mf->size;
        if (FIRST_FEW_BYTES < sz)
                sz = FIRST_FEW_BYTES;
        if (memchr(mf->ptr, 0, sz))
                return 1;
        return 0;
}

static void builtin_diff(const char *name_a,
                         const char *name_b,
                         struct diff_filespec *one,
                         struct diff_filespec *two,
                         const char *xfrm_msg,
                         int complete_rewrite)
{
        mmfile_t mf1, mf2;
        const char *lbl[2];
        char *a_one, *b_two;

        a_one = quote_two("a/", name_a);
        b_two = quote_two("b/", name_b);
        lbl[0] = DIFF_FILE_VALID(one) ? a_one : "/dev/null";
        lbl[1] = DIFF_FILE_VALID(two) ? b_two : "/dev/null";
        printf("diff --git %s %s\n", a_one, b_two);
        if (lbl[0][0] == '/') {
                /* /dev/null */
                printf("new file mode %06o\n", two->mode);
                if (xfrm_msg && xfrm_msg[0])
                        puts(xfrm_msg);
        }
        else if (lbl[1][0] == '/') {
                printf("deleted file mode %06o\n", one->mode);
                if (xfrm_msg && xfrm_msg[0])
                        puts(xfrm_msg);
        }
        else {
                if (one->mode != two->mode) {
                        printf("old mode %06o\n", one->mode);
                        printf("new mode %06o\n", two->mode);
                }
                if (xfrm_msg && xfrm_msg[0])
                        puts(xfrm_msg);
                /*
                 * we do not run diff between different kind
                 * of objects.
                 */
                if ((one->mode ^ two->mode) & S_IFMT)
                        goto free_ab_and_return;
                if (complete_rewrite) {
                        emit_rewrite_diff(name_a, name_b, one, two);
                        goto free_ab_and_return;
                }
        }

        if (fill_mmfile(&mf1, one) < 0 || fill_mmfile(&mf2, two) < 0)
                die("unable to read files to diff");

        if (mmfile_is_binary(&mf1) || mmfile_is_binary(&mf2))
                printf("Binary files %s and %s differ\n", lbl[0], lbl[1]);
        else {
                /* Crazy xdl interfaces.. */
                const char *diffopts = getenv("GIT_DIFF_OPTS");
                xpparam_t xpp;
                xdemitconf_t xecfg;
                xdemitcb_t ecb;
                struct emit_callback ecbdata;

                ecbdata.label_path = lbl;
                xpp.flags = XDF_NEED_MINIMAL;
                xecfg.ctxlen = 3;
                xecfg.flags = XDL_EMIT_FUNCNAMES;
                if (!diffopts)
                        ;
                else if (!strncmp(diffopts, "--unified=", 10))
                        xecfg.ctxlen = strtoul(diffopts + 10, NULL, 10);
                else if (!strncmp(diffopts, "-u", 2))
                        xecfg.ctxlen = strtoul(diffopts + 2, NULL, 10);
                ecb.outf = fn_out;
                ecb.priv = &ecbdata;
                xdl_diff(&mf1, &mf2, &xpp, &xecfg, &ecb);
        }

 free_ab_and_return:
        free(a_one);
        free(b_two);
        return;
}

static void builtin_diffstat(const char *name_a, const char *name_b,
                struct diff_filespec *one, struct diff_filespec *two,
                struct diffstat_t *diffstat)
{
        mmfile_t mf1, mf2;
        struct diffstat_file *data;

        data = diffstat_add(diffstat, name_a ? name_a : name_b);

        if (fill_mmfile(&mf1, one) < 0 || fill_mmfile(&mf2, two) < 0)
                die("unable to read files to diff");

        if (mmfile_is_binary(&mf1) || mmfile_is_binary(&mf2))
                data->added = -1;
        else {
                /* Crazy xdl interfaces.. */
                xpparam_t xpp;
                xdemitconf_t xecfg;
                xdemitcb_t ecb;

                xpp.flags = XDF_NEED_MINIMAL;
                xecfg.ctxlen = 3;
                xecfg.flags = XDL_EMIT_FUNCNAMES;
                ecb.outf = xdiff_outf;
                ecb.priv = diffstat;
                xdl_diff(&mf1, &mf2, &xpp, &xecfg, &ecb);
        }
}

struct diff_filespec *alloc_filespec(const char *path)
{
        int namelen = strlen(path);
        struct diff_filespec *spec = xmalloc(sizeof(*spec) + namelen + 1);

        memset(spec, 0, sizeof(*spec));
        spec->path = (char *)(spec + 1);
        memcpy(spec->path, path, namelen+1);
        return spec;
}

void fill_filespec(struct diff_filespec *spec, const unsigned char *sha1,
                   unsigned short mode)
{
        if (mode) {
                spec->mode = canon_mode(mode);
                memcpy(spec->sha1, sha1, 20);
                spec->sha1_valid = !!memcmp(sha1, null_sha1, 20);
        }
}

/*
 * Given a name and sha1 pair, if the dircache tells us the file in
 * the work tree has that object contents, return true, so that
 * prepare_temp_file() does not have to inflate and extract.
 */
static int work_tree_matches(const char *name, const unsigned char *sha1)
{
        struct cache_entry *ce;
        struct stat st;
        int pos, len;

        /* We do not read the cache ourselves here, because the
         * benchmark with my previous version that always reads cache
         * shows that it makes things worse for diff-tree comparing
         * two linux-2.6 kernel trees in an already checked out work
         * tree.  This is because most diff-tree comparisons deal with
         * only a small number of files, while reading the cache is
         * expensive for a large project, and its cost outweighs the
         * savings we get by not inflating the object to a temporary
         * file.  Practically, this code only helps when we are used
         * by diff-cache --cached, which does read the cache before
         * calling us.
         */
        if (!active_cache)
                return 0;

        len = strlen(name);
        pos = cache_name_pos(name, len);
        if (pos < 0)
                return 0;
        ce = active_cache[pos];
        if ((lstat(name, &st) < 0) ||
            !S_ISREG(st.st_mode) || /* careful! */
            ce_match_stat(ce, &st, 0) ||
            memcmp(sha1, ce->sha1, 20))
                return 0;
        /* we return 1 only when we can stat, it is a regular file,
         * stat information matches, and sha1 recorded in the cache
         * matches.  I.e. we know the file in the work tree really is
         * the same as the <name, sha1> pair.
         */
        return 1;
}

static struct sha1_size_cache {
        unsigned char sha1[20];
        unsigned long size;
} **sha1_size_cache;
static int sha1_size_cache_nr, sha1_size_cache_alloc;

static struct sha1_size_cache *locate_size_cache(unsigned char *sha1,
                                                 int find_only,
                                                 unsigned long size)
{
        int first, last;
        struct sha1_size_cache *e;

        first = 0;
        last = sha1_size_cache_nr;
        while (last > first) {
                int cmp, next = (last + first) >> 1;
                e = sha1_size_cache[next];
                cmp = memcmp(e->sha1, sha1, 20);
                if (!cmp)
                        return e;
                if (cmp < 0) {
                        last = next;
                        continue;
                }
                first = next+1;
        }
        /* not found */
        if (find_only)
                return NULL;
        /* insert to make it at "first" */
        if (sha1_size_cache_alloc <= sha1_size_cache_nr) {
                sha1_size_cache_alloc = alloc_nr(sha1_size_cache_alloc);
                sha1_size_cache = xrealloc(sha1_size_cache,
                                           sha1_size_cache_alloc *
                                           sizeof(*sha1_size_cache));
        }
        sha1_size_cache_nr++;
        if (first < sha1_size_cache_nr)
                memmove(sha1_size_cache + first + 1, sha1_size_cache + first,
                        (sha1_size_cache_nr - first - 1) *
                        sizeof(*sha1_size_cache));
        e = xmalloc(sizeof(struct sha1_size_cache));
        sha1_size_cache[first] = e;
        memcpy(e->sha1, sha1, 20);
        e->size = size;
        return e;
}

/*
 * While doing rename detection and pickaxe operation, we may need to
 * grab the data for the blob (or file) for our own in-core comparison.
 * diff_filespec has data and size fields for this purpose.
 */
int diff_populate_filespec(struct diff_filespec *s, int size_only)
{
        int err = 0;
        if (!DIFF_FILE_VALID(s))
                die("internal error: asking to populate invalid file.");
        if (S_ISDIR(s->mode))
                return -1;

        if (!use_size_cache)
                size_only = 0;

        if (s->data)
                return err;
        if (!s->sha1_valid ||
            work_tree_matches(s->path, s->sha1)) {
                struct stat st;
                int fd;
                if (lstat(s->path, &st) < 0) {
                        if (errno == ENOENT) {
                        err_empty:
                                err = -1;
                        empty:
                                s->data = "";
                                s->size = 0;
                                return err;
                        }
                }
                s->size = st.st_size;
                if (!s->size)
                        goto empty;
                if (size_only)
                        return 0;
                if (S_ISLNK(st.st_mode)) {
                        int ret;
                        s->data = xmalloc(s->size);
                        s->should_free = 1;
                        ret = readlink(s->path, s->data, s->size);
                        if (ret < 0) {
                                free(s->data);
                                goto err_empty;
                        }
                        return 0;
                }
                fd = open(s->path, O_RDONLY);
                if (fd < 0)
                        goto err_empty;
                s->data = mmap(NULL, s->size, PROT_READ, MAP_PRIVATE, fd, 0);
                close(fd);
                if (s->data == MAP_FAILED)
                        goto err_empty;
                s->should_munmap = 1;
        }
        else {
                char type[20];
                struct sha1_size_cache *e;

                if (size_only) {
                        e = locate_size_cache(s->sha1, 1, 0);
                        if (e) {
                                s->size = e->size;
                                return 0;
                        }
                        if (!sha1_object_info(s->sha1, type, &s->size))
                                locate_size_cache(s->sha1, 0, s->size);
                }
                else {
                        s->data = read_sha1_file(s->sha1, type, &s->size);
                        s->should_free = 1;
                }
        }
        return 0;
}

void diff_free_filespec_data(struct diff_filespec *s)
{
        if (s->should_free)
                free(s->data);
        else if (s->should_munmap)
                munmap(s->data, s->size);
        s->should_free = s->should_munmap = 0;
        s->data = NULL;
        free(s->cnt_data);
        s->cnt_data = NULL;
}

static void prep_temp_blob(struct diff_tempfile *temp,
                           void *blob,
                           unsigned long size,
                           const unsigned char *sha1,
                           int mode)
{
        int fd;

        fd = git_mkstemp(temp->tmp_path, TEMPFILE_PATH_LEN, ".diff_XXXXXX");
        if (fd < 0)
                die("unable to create temp-file");
        if (write(fd, blob, size) != size)
                die("unable to write temp-file");
        close(fd);
        temp->name = temp->tmp_path;
        strcpy(temp->hex, sha1_to_hex(sha1));
        temp->hex[40] = 0;
        sprintf(temp->mode, "%06o", mode);
}

static void prepare_temp_file(const char *name,
                              struct diff_tempfile *temp,
                              struct diff_filespec *one)
{
        if (!DIFF_FILE_VALID(one)) {
        not_a_valid_file:
                /* A '-' entry produces this for file-2, and
                 * a '+' entry produces this for file-1.
                 */
                temp->name = "/dev/null";
                strcpy(temp->hex, ".");
                strcpy(temp->mode, ".");
                return;
        }

        if (!one->sha1_valid ||
            work_tree_matches(name, one->sha1)) {
                struct stat st;
                if (lstat(name, &st) < 0) {
                        if (errno == ENOENT)
                                goto not_a_valid_file;
                        die("stat(%s): %s", name, strerror(errno));
                }
                if (S_ISLNK(st.st_mode)) {
                        int ret;
                        char buf[PATH_MAX + 1]; /* ought to be SYMLINK_MAX */
                        if (sizeof(buf) <= st.st_size)
                                die("symlink too long: %s", name);
                        ret = readlink(name, buf, st.st_size);
                        if (ret < 0)
                                die("readlink(%s)", name);
                        prep_temp_blob(temp, buf, st.st_size,
                                       (one->sha1_valid ?
                                        one->sha1 : null_sha1),
                                       (one->sha1_valid ?
                                        one->mode : S_IFLNK));
                }
                else {
                        /* we can borrow from the file in the work tree */
                        temp->name = name;
                        if (!one->sha1_valid)
                                strcpy(temp->hex, sha1_to_hex(null_sha1));
                        else
                                strcpy(temp->hex, sha1_to_hex(one->sha1));
                        /* Even though we may sometimes borrow the
                         * contents from the work tree, we always want
                         * one->mode.  mode is trustworthy even when
                         * !(one->sha1_valid), as long as
                         * DIFF_FILE_VALID(one).
                         */
                        sprintf(temp->mode, "%06o", one->mode);
                }
                return;
        }
        else {
                if (diff_populate_filespec(one, 0))
                        die("cannot read data blob for %s", one->path);
                prep_temp_blob(temp, one->data, one->size,
                               one->sha1, one->mode);
        }
}

static void remove_tempfile(void)
{
        int i;

        for (i = 0; i < 2; i++)
                if (diff_temp[i].name == diff_temp[i].tmp_path) {
                        unlink(diff_temp[i].name);
                        diff_temp[i].name = NULL;
                }
}

static void remove_tempfile_on_signal(int signo)
{
        remove_tempfile();
        signal(SIGINT, SIG_DFL);
        raise(signo);
}

static int spawn_prog(const char *pgm, const char **arg)
{
        pid_t pid;
        int status;

        fflush(NULL);
        pid = fork();
        if (pid < 0)
                die("unable to fork");
        if (!pid) {
                execvp(pgm, (char *const*) arg);
                exit(255);
        }

        while (waitpid(pid, &status, 0) < 0) {
                if (errno == EINTR)
                        continue;
                return -1;
        }

        /* Earlier we did not check the exit status because
         * diff exits non-zero if files are different, and
         * we are not interested in knowing that.  It was a
         * mistake which made it harder to quit a diff-*
         * session that uses the git-apply-patch-script as
         * the GIT_EXTERNAL_DIFF.  A custom GIT_EXTERNAL_DIFF
         * should also exit non-zero only when it wants to
         * abort the entire diff-* session.
         */
        if (WIFEXITED(status) && !WEXITSTATUS(status))
                return 0;
        return -1;
}

/* An external diff command takes:
 *
 * diff-cmd name infile1 infile1-sha1 infile1-mode \
 *               infile2 infile2-sha1 infile2-mode [ rename-to ]
 *
 */
static void run_external_diff(const char *pgm,
                              const char *name,
                              const char *other,
                              struct diff_filespec *one,
                              struct diff_filespec *two,
                              const char *xfrm_msg,
                              int complete_rewrite)
{
        const char *spawn_arg[10];
        struct diff_tempfile *temp = diff_temp;
        int retval;
        static int atexit_asked = 0;
        const char *othername;
        const char **arg = &spawn_arg[0];

        othername = (other? other : name);
        if (one && two) {
                prepare_temp_file(name, &temp[0], one);
                prepare_temp_file(othername, &temp[1], two);
                if (! atexit_asked &&
                    (temp[0].name == temp[0].tmp_path ||
                     temp[1].name == temp[1].tmp_path)) {
                        atexit_asked = 1;
                        atexit(remove_tempfile);
                }
                signal(SIGINT, remove_tempfile_on_signal);
        }

        if (one && two) {
                *arg++ = pgm;
                *arg++ = name;
                *arg++ = temp[0].name;
                *arg++ = temp[0].hex;
                *arg++ = temp[0].mode;
                *arg++ = temp[1].name;
                *arg++ = temp[1].hex;
                *arg++ = temp[1].mode;
                if (other) {
                        *arg++ = other;
                        *arg++ = xfrm_msg;
                }
        } else {
                *arg++ = pgm;
                *arg++ = name;
        }
        *arg = NULL;
        retval = spawn_prog(pgm, spawn_arg);
        remove_tempfile();
        if (retval) {
                fprintf(stderr, "external diff died, stopping at %s.\n", name);
                exit(1);
        }
}

static void run_diff_cmd(const char *pgm,
                         const char *name,
                         const char *other,
                         struct diff_filespec *one,
                         struct diff_filespec *two,
                         const char *xfrm_msg,
                         int complete_rewrite)
{
        if (pgm) {
                run_external_diff(pgm, name, other, one, two, xfrm_msg,
                                  complete_rewrite);
                return;
        }
        if (one && two)
                builtin_diff(name, other ? other : name,
                             one, two, xfrm_msg, complete_rewrite);
        else
                printf("* Unmerged path %s\n", name);
}

static void diff_fill_sha1_info(struct diff_filespec *one)
{
        if (DIFF_FILE_VALID(one)) {
                if (!one->sha1_valid) {
                        struct stat st;
                        if (lstat(one->path, &st) < 0)
                                die("stat %s", one->path);
                        if (index_path(one->sha1, one->path, &st, 0))
                                die("cannot hash %s\n", one->path);
                }
        }
        else
                memset(one->sha1, 0, 20);
}

static void run_diff(struct diff_filepair *p, struct diff_options *o)
{
        const char *pgm = external_diff();
        char msg[PATH_MAX*2+300], *xfrm_msg;
        struct diff_filespec *one;
        struct diff_filespec *two;
        const char *name;
        const char *other;
        char *name_munged, *other_munged;
        int complete_rewrite = 0;
        int len;

        if (DIFF_PAIR_UNMERGED(p)) {
                /* unmerged */
                run_diff_cmd(pgm, p->one->path, NULL, NULL, NULL, NULL, 0);
                return;
        }

        name = p->one->path;
        other = (strcmp(name, p->two->path) ? p->two->path : NULL);
        name_munged = quote_one(name);
        other_munged = quote_one(other);
        one = p->one; two = p->two;

        diff_fill_sha1_info(one);
        diff_fill_sha1_info(two);

        len = 0;
        switch (p->status) {
        case DIFF_STATUS_COPIED:
                len += snprintf(msg + len, sizeof(msg) - len,
                                "similarity index %d%%\n"
                                "copy from %s\n"
                                "copy to %s\n",
                                (int)(0.5 + p->score * 100.0/MAX_SCORE),
                                name_munged, other_munged);
                break;
        case DIFF_STATUS_RENAMED:
                len += snprintf(msg + len, sizeof(msg) - len,
                                "similarity index %d%%\n"
                                "rename from %s\n"
                                "rename to %s\n",
                                (int)(0.5 + p->score * 100.0/MAX_SCORE),
                                name_munged, other_munged);
                break;
        case DIFF_STATUS_MODIFIED:
                if (p->score) {
                        len += snprintf(msg + len, sizeof(msg) - len,
                                        "dissimilarity index %d%%\n",
                                        (int)(0.5 + p->score *
                                              100.0/MAX_SCORE));
                        complete_rewrite = 1;
                        break;
                }
                /* fallthru */
        default:
                /* nothing */
                ;
        }

        if (memcmp(one->sha1, two->sha1, 20)) {
                char one_sha1[41];
                int abbrev = o->full_index ? 40 : DEFAULT_ABBREV;
                memcpy(one_sha1, sha1_to_hex(one->sha1), 41);

                len += snprintf(msg + len, sizeof(msg) - len,
                                "index %.*s..%.*s",
                                abbrev, one_sha1, abbrev,
                                sha1_to_hex(two->sha1));
                if (one->mode == two->mode)
                        len += snprintf(msg + len, sizeof(msg) - len,
                                        " %06o", one->mode);
                len += snprintf(msg + len, sizeof(msg) - len, "\n");
        }

        if (len)
                msg[--len] = 0;
        xfrm_msg = len ? msg : NULL;

        if (!pgm &&
            DIFF_FILE_VALID(one) && DIFF_FILE_VALID(two) &&
            (S_IFMT & one->mode) != (S_IFMT & two->mode)) {
                /* a filepair that changes between file and symlink
                 * needs to be split into deletion and creation.
                 */
                struct diff_filespec *null = alloc_filespec(two->path);
                run_diff_cmd(NULL, name, other, one, null, xfrm_msg, 0);
                free(null);
                null = alloc_filespec(one->path);
                run_diff_cmd(NULL, name, other, null, two, xfrm_msg, 0);
                free(null);
        }
        else
                run_diff_cmd(pgm, name, other, one, two, xfrm_msg,
                             complete_rewrite);

        free(name_munged);
        free(other_munged);
}

static void run_diffstat(struct diff_filepair *p, struct diff_options *o,
                struct diffstat_t *diffstat)
{
        const char *name;
        const char *other;

        if (DIFF_PAIR_UNMERGED(p)) {
                /* unmerged */
                builtin_diffstat(p->one->path, NULL, NULL, NULL, diffstat);
                return;
        }

        name = p->one->path;
        other = (strcmp(name, p->two->path) ? p->two->path : NULL);

        diff_fill_sha1_info(p->one);
        diff_fill_sha1_info(p->two);

        builtin_diffstat(name, other, p->one, p->two, diffstat);
}

void diff_setup(struct diff_options *options)
{
        memset(options, 0, sizeof(*options));
        options->output_format = DIFF_FORMAT_RAW;
        options->line_termination = '\n';
        options->break_opt = -1;
        options->rename_limit = -1;

        options->change = diff_change;
        options->add_remove = diff_addremove;
}

int diff_setup_done(struct diff_options *options)
{
        if ((options->find_copies_harder &&
             options->detect_rename != DIFF_DETECT_COPY) ||
            (0 <= options->rename_limit && !options->detect_rename))
                return -1;
        if (options->detect_rename && options->rename_limit < 0)
                options->rename_limit = diff_rename_limit_default;
        if (options->setup & DIFF_SETUP_USE_CACHE) {
                if (!active_cache)
                        /* read-cache does not die even when it fails
                         * so it is safe for us to do this here.  Also
                         * it does not smudge active_cache or active_nr
                         * when it fails, so we do not have to worry about
                         * cleaning it up ourselves either.
                         */
                        read_cache();
        }
        if (options->setup & DIFF_SETUP_USE_SIZE_CACHE)
                use_size_cache = 1;
        if (options->abbrev <= 0 || 40 < options->abbrev)
                options->abbrev = 40; /* full */

        return 0;
}

int diff_opt_parse(struct diff_options *options, const char **av, int ac)
{
        const char *arg = av[0];
        if (!strcmp(arg, "-p") || !strcmp(arg, "-u"))
                options->output_format = DIFF_FORMAT_PATCH;
        else if (!strcmp(arg, "--patch-with-raw")) {
                options->output_format = DIFF_FORMAT_PATCH;
                options->with_raw = 1;
        }
        else if (!strcmp(arg, "--stat"))
                options->output_format = DIFF_FORMAT_DIFFSTAT;
        else if (!strcmp(arg, "-z"))
                options->line_termination = 0;
        else if (!strncmp(arg, "-l", 2))
                options->rename_limit = strtoul(arg+2, NULL, 10);
        else if (!strcmp(arg, "--full-index"))
                options->full_index = 1;
        else if (!strcmp(arg, "--name-only"))
                options->output_format = DIFF_FORMAT_NAME;
        else if (!strcmp(arg, "--name-status"))
                options->output_format = DIFF_FORMAT_NAME_STATUS;
        else if (!strcmp(arg, "-R"))
                options->reverse_diff = 1;
        else if (!strncmp(arg, "-S", 2))
                options->pickaxe = arg + 2;
        else if (!strcmp(arg, "-s"))
                options->output_format = DIFF_FORMAT_NO_OUTPUT;
        else if (!strncmp(arg, "-O", 2))
                options->orderfile = arg + 2;
        else if (!strncmp(arg, "--diff-filter=", 14))
                options->filter = arg + 14;
        else if (!strcmp(arg, "--pickaxe-all"))
                options->pickaxe_opts = DIFF_PICKAXE_ALL;
        else if (!strcmp(arg, "--pickaxe-regex"))
                options->pickaxe_opts = DIFF_PICKAXE_REGEX;
        else if (!strncmp(arg, "-B", 2)) {
                if ((options->break_opt =
                     diff_scoreopt_parse(arg)) == -1)
                        return -1;
        }
        else if (!strncmp(arg, "-M", 2)) {
                if ((options->rename_score =
                     diff_scoreopt_parse(arg)) == -1)
                        return -1;
                options->detect_rename = DIFF_DETECT_RENAME;
        }
        else if (!strncmp(arg, "-C", 2)) {
                if ((options->rename_score =
                     diff_scoreopt_parse(arg)) == -1)
                        return -1;
                options->detect_rename = DIFF_DETECT_COPY;
        }
        else if (!strcmp(arg, "--find-copies-harder"))
                options->find_copies_harder = 1;
        else if (!strcmp(arg, "--abbrev"))
                options->abbrev = DEFAULT_ABBREV;
        else if (!strncmp(arg, "--abbrev=", 9)) {
                options->abbrev = strtoul(arg + 9, NULL, 10);
                if (options->abbrev < MINIMUM_ABBREV)
                        options->abbrev = MINIMUM_ABBREV;
                else if (40 < options->abbrev)
                        options->abbrev = 40;
        }
        else
                return 0;
        return 1;
}

static int parse_num(const char **cp_p)
{
        unsigned long num, scale;
        int ch, dot;
        const char *cp = *cp_p;

        num = 0;
        scale = 1;
        dot = 0;
        for(;;) {
                ch = *cp;
                if ( !dot && ch == '.' ) {
                        scale = 1;
                        dot = 1;
                } else if ( ch == '%' ) {
                        scale = dot ? scale*100 : 100;
                        cp++;   /* % is always at the end */
                        break;
                } else if ( ch >= '0' && ch <= '9' ) {
                        if ( scale < 100000 ) {
                                scale *= 10;
                                num = (num*10) + (ch-'0');
                        }
                } else {
                        break;
                }
                cp++;
        }
        *cp_p = cp;

        /* user says num divided by scale and we say internally that
         * is MAX_SCORE * num / scale.
         */
        return (num >= scale) ? MAX_SCORE : (MAX_SCORE * num / scale);
}

int diff_scoreopt_parse(const char *opt)
{
        int opt1, opt2, cmd;

        if (*opt++ != '-')
                return -1;
        cmd = *opt++;
        if (cmd != 'M' && cmd != 'C' && cmd != 'B')
                return -1; /* that is not a -M, -C nor -B option */

        opt1 = parse_num(&opt);
        if (cmd != 'B')
                opt2 = 0;
        else {
                if (*opt == 0)
                        opt2 = 0;
                else if (*opt != '/')
                        return -1; /* we expect -B80/99 or -B80 */
                else {
                        opt++;
                        opt2 = parse_num(&opt);
                }
        }
        if (*opt != 0)
                return -1;
        return opt1 | (opt2 << 16);
}

struct diff_queue_struct diff_queued_diff;

void diff_q(struct diff_queue_struct *queue, struct diff_filepair *dp)
{
        if (queue->alloc <= queue->nr) {
                queue->alloc = alloc_nr(queue->alloc);
                queue->queue = xrealloc(queue->queue,
                                        sizeof(dp) * queue->alloc);
        }
        queue->queue[queue->nr++] = dp;
}

struct diff_filepair *diff_queue(struct diff_queue_struct *queue,
                                 struct diff_filespec *one,
                                 struct diff_filespec *two)
{
        struct diff_filepair *dp = xmalloc(sizeof(*dp));
        dp->one = one;
        dp->two = two;
        dp->score = 0;
        dp->status = 0;
        dp->source_stays = 0;
        dp->broken_pair = 0;
        if (queue)
                diff_q(queue, dp);
        return dp;
}

void diff_free_filepair(struct diff_filepair *p)
{
        diff_free_filespec_data(p->one);
        diff_free_filespec_data(p->two);
        free(p->one);
        free(p->two);
        free(p);
}

/* This is different from find_unique_abbrev() in that
 * it stuffs the result with dots for alignment.
 */
const char *diff_unique_abbrev(const unsigned char *sha1, int len)
{
        int abblen;
        const char *abbrev;
        if (len == 40)
                return sha1_to_hex(sha1);

        abbrev = find_unique_abbrev(sha1, len);
        if (!abbrev)
                return sha1_to_hex(sha1);
        abblen = strlen(abbrev);
        if (abblen < 37) {
                static char hex[41];
                if (len < abblen && abblen <= len + 2)
                        sprintf(hex, "%s%.*s", abbrev, len+3-abblen, "..");
                else
                        sprintf(hex, "%s...", abbrev);
                return hex;
        }
        return sha1_to_hex(sha1);
}

static void diff_flush_raw(struct diff_filepair *p,
                           int line_termination,
                           int inter_name_termination,
                           struct diff_options *options,
                           int output_format)
{
        int two_paths;
        char status[10];
        int abbrev = options->abbrev;
        const char *path_one, *path_two;

        path_one = p->one->path;
        path_two = p->two->path;
        if (line_termination) {
                path_one = quote_one(path_one);
                path_two = quote_one(path_two);
        }

        if (p->score)
                sprintf(status, "%c%03d", p->status,
                        (int)(0.5 + p->score * 100.0/MAX_SCORE));
        else {
                status[0] = p->status;
                status[1] = 0;
        }
        switch (p->status) {
        case DIFF_STATUS_COPIED:
        case DIFF_STATUS_RENAMED:
                two_paths = 1;
                break;
        case DIFF_STATUS_ADDED:
        case DIFF_STATUS_DELETED:
                two_paths = 0;
                break;
        default:
                two_paths = 0;
                break;
        }
        if (output_format != DIFF_FORMAT_NAME_STATUS) {
                printf(":%06o %06o %s ",
                       p->one->mode, p->two->mode,
                       diff_unique_abbrev(p->one->sha1, abbrev));
                printf("%s ",
                       diff_unique_abbrev(p->two->sha1, abbrev));
        }
        printf("%s%c%s", status, inter_name_termination, path_one);
        if (two_paths)
                printf("%c%s", inter_name_termination, path_two);
        putchar(line_termination);
        if (path_one != p->one->path)
                free((void*)path_one);
        if (path_two != p->two->path)
                free((void*)path_two);
}

static void diff_flush_name(struct diff_filepair *p,
                            int inter_name_termination,
                            int line_termination)
{
        char *path = p->two->path;

        if (line_termination)
                path = quote_one(p->two->path);
        else
                path = p->two->path;
        printf("%s%c", path, line_termination);
        if (p->two->path != path)
                free(path);
}

int diff_unmodified_pair(struct diff_filepair *p)
{
        /* This function is written stricter than necessary to support
         * the currently implemented transformers, but the idea is to
         * let transformers to produce diff_filepairs any way they want,
         * and filter and clean them up here before producing the output.
         */
        struct diff_filespec *one, *two;

        if (DIFF_PAIR_UNMERGED(p))
                return 0; /* unmerged is interesting */

        one = p->one;
        two = p->two;

        /* deletion, addition, mode or type change
         * and rename are all interesting.
         */
        if (DIFF_FILE_VALID(one) != DIFF_FILE_VALID(two) ||
            DIFF_PAIR_MODE_CHANGED(p) ||
            strcmp(one->path, two->path))
                return 0;

        /* both are valid and point at the same path.  that is, we are
         * dealing with a change.
         */
        if (one->sha1_valid && two->sha1_valid &&
            !memcmp(one->sha1, two->sha1, sizeof(one->sha1)))
                return 1; /* no change */
        if (!one->sha1_valid && !two->sha1_valid)
                return 1; /* both look at the same file on the filesystem. */
        return 0;
}

static void diff_flush_patch(struct diff_filepair *p, struct diff_options *o)
{
        if (diff_unmodified_pair(p))
                return;

        if ((DIFF_FILE_VALID(p->one) && S_ISDIR(p->one->mode)) ||
            (DIFF_FILE_VALID(p->two) && S_ISDIR(p->two->mode)))
                return; /* no tree diffs in patch format */

        run_diff(p, o);
}

static void diff_flush_stat(struct diff_filepair *p, struct diff_options *o,
                struct diffstat_t *diffstat)
{
        if (diff_unmodified_pair(p))
                return;

        if ((DIFF_FILE_VALID(p->one) && S_ISDIR(p->one->mode)) ||
            (DIFF_FILE_VALID(p->two) && S_ISDIR(p->two->mode)))
                return; /* no tree diffs in patch format */

        run_diffstat(p, o, diffstat);
}

int diff_queue_is_empty(void)
{
        struct diff_queue_struct *q = &diff_queued_diff;
        int i;
        for (i = 0; i < q->nr; i++)
                if (!diff_unmodified_pair(q->queue[i]))
                        return 0;
        return 1;
}

#if DIFF_DEBUG
void diff_debug_filespec(struct diff_filespec *s, int x, const char *one)
{
        fprintf(stderr, "queue[%d] %s (%s) %s %06o %s\n",
                x, one ? one : "",
                s->path,
                DIFF_FILE_VALID(s) ? "valid" : "invalid",
                s->mode,
                s->sha1_valid ? sha1_to_hex(s->sha1) : "");
        fprintf(stderr, "queue[%d] %s size %lu flags %d\n",
                x, one ? one : "",
                s->size, s->xfrm_flags);
}

void diff_debug_filepair(const struct diff_filepair *p, int i)
{
        diff_debug_filespec(p->one, i, "one");
        diff_debug_filespec(p->two, i, "two");
        fprintf(stderr, "score %d, status %c stays %d broken %d\n",
                p->score, p->status ? p->status : '?',
                p->source_stays, p->broken_pair);
}

void diff_debug_queue(const char *msg, struct diff_queue_struct *q)
{
        int i;
        if (msg)
                fprintf(stderr, "%s\n", msg);
        fprintf(stderr, "q->nr = %d\n", q->nr);
        for (i = 0; i < q->nr; i++) {
                struct diff_filepair *p = q->queue[i];
                diff_debug_filepair(p, i);
        }
}
#endif

static void diff_resolve_rename_copy(void)
{
        int i, j;
        struct diff_filepair *p, *pp;
        struct diff_queue_struct *q = &diff_queued_diff;

        diff_debug_queue("resolve-rename-copy", q);

        for (i = 0; i < q->nr; i++) {
                p = q->queue[i];
                p->status = 0; /* undecided */
                if (DIFF_PAIR_UNMERGED(p))
                        p->status = DIFF_STATUS_UNMERGED;
                else if (!DIFF_FILE_VALID(p->one))
                        p->status = DIFF_STATUS_ADDED;
                else if (!DIFF_FILE_VALID(p->two))
                        p->status = DIFF_STATUS_DELETED;
                else if (DIFF_PAIR_TYPE_CHANGED(p))
                        p->status = DIFF_STATUS_TYPE_CHANGED;

                /* from this point on, we are dealing with a pair
                 * whose both sides are valid and of the same type, i.e.
                 * either in-place edit or rename/copy edit.
                 */
                else if (DIFF_PAIR_RENAME(p)) {
                        if (p->source_stays) {
                                p->status = DIFF_STATUS_COPIED;
                                continue;
                        }
                        /* See if there is some other filepair that
                         * copies from the same source as us.  If so
                         * we are a copy.  Otherwise we are either a
                         * copy if the path stays, or a rename if it
                         * does not, but we already handled "stays" case.
                         */
                        for (j = i + 1; j < q->nr; j++) {
                                pp = q->queue[j];
                                if (strcmp(pp->one->path, p->one->path))
                                        continue; /* not us */
                                if (!DIFF_PAIR_RENAME(pp))
                                        continue; /* not a rename/copy */
                                /* pp is a rename/copy from the same source */
                                p->status = DIFF_STATUS_COPIED;
                                break;
                        }
                        if (!p->status)
                                p->status = DIFF_STATUS_RENAMED;
                }
                else if (memcmp(p->one->sha1, p->two->sha1, 20) ||
                         p->one->mode != p->two->mode)
                        p->status = DIFF_STATUS_MODIFIED;
                else {
                        /* This is a "no-change" entry and should not
                         * happen anymore, but prepare for broken callers.
                         */
                        error("feeding unmodified %s to diffcore",
                              p->one->path);
                        p->status = DIFF_STATUS_UNKNOWN;
                }
        }
        diff_debug_queue("resolve-rename-copy done", q);
}

static void flush_one_pair(struct diff_filepair *p,
                           int diff_output_format,
                           struct diff_options *options,
                           struct diffstat_t *diffstat)
{
        int inter_name_termination = '\t';
        int line_termination = options->line_termination;
        if (!line_termination)
                inter_name_termination = 0;

        switch (p->status) {
        case DIFF_STATUS_UNKNOWN:
                break;
        case 0:
                die("internal error in diff-resolve-rename-copy");
                break;
        default:
                switch (diff_output_format) {
                case DIFF_FORMAT_DIFFSTAT:
                        diff_flush_stat(p, options, diffstat);
                        break;
                case DIFF_FORMAT_PATCH:
                        diff_flush_patch(p, options);
                        break;
                case DIFF_FORMAT_RAW:
                case DIFF_FORMAT_NAME_STATUS:
                        diff_flush_raw(p, line_termination,
                                       inter_name_termination,
                                       options, diff_output_format);
                        break;
                case DIFF_FORMAT_NAME:
                        diff_flush_name(p,
                                        inter_name_termination,
                                        line_termination);
                        break;
                case DIFF_FORMAT_NO_OUTPUT:
                        break;
                }
        }
}

void diff_flush(struct diff_options *options)
{
        struct diff_queue_struct *q = &diff_queued_diff;
        int i;
        int diff_output_format = options->output_format;
        struct diffstat_t *diffstat = NULL;

        if (diff_output_format == DIFF_FORMAT_DIFFSTAT) {
                diffstat = xcalloc(sizeof (struct diffstat_t), 1);
                diffstat->xm.consume = diffstat_consume;
        }

        if (options->with_raw) {
                for (i = 0; i < q->nr; i++) {
                        struct diff_filepair *p = q->queue[i];
                        flush_one_pair(p, DIFF_FORMAT_RAW, options, NULL);
                }
                putchar(options->line_termination);
        }
        for (i = 0; i < q->nr; i++) {
                struct diff_filepair *p = q->queue[i];
                flush_one_pair(p, diff_output_format, options, diffstat);
                diff_free_filepair(p);
        }

        if (diffstat) {
                show_stats(diffstat);
                free(diffstat);
        }

        free(q->queue);
        q->queue = NULL;
        q->nr = q->alloc = 0;
}

static void diffcore_apply_filter(const char *filter)
{
        int i;
        struct diff_queue_struct *q = &diff_queued_diff;
        struct diff_queue_struct outq;
        outq.queue = NULL;
        outq.nr = outq.alloc = 0;

        if (!filter)
                return;

        if (strchr(filter, DIFF_STATUS_FILTER_AON)) {
                int found;
                for (i = found = 0; !found && i < q->nr; i++) {
                        struct diff_filepair *p = q->queue[i];
                        if (((p->status == DIFF_STATUS_MODIFIED) &&
                             ((p->score &&
                               strchr(filter, DIFF_STATUS_FILTER_BROKEN)) ||
                              (!p->score &&
                               strchr(filter, DIFF_STATUS_MODIFIED)))) ||
                            ((p->status != DIFF_STATUS_MODIFIED) &&
                             strchr(filter, p->status)))
                                found++;
                }
                if (found)
                        return;

                /* otherwise we will clear the whole queue
                 * by copying the empty outq at the end of this
                 * function, but first clear the current entries
                 * in the queue.
                 */
                for (i = 0; i < q->nr; i++)
                        diff_free_filepair(q->queue[i]);
        }
        else {
                /* Only the matching ones */
                for (i = 0; i < q->nr; i++) {
                        struct diff_filepair *p = q->queue[i];

                        if (((p->status == DIFF_STATUS_MODIFIED) &&
                             ((p->score &&
                               strchr(filter, DIFF_STATUS_FILTER_BROKEN)) ||
                              (!p->score &&
                               strchr(filter, DIFF_STATUS_MODIFIED)))) ||
                            ((p->status != DIFF_STATUS_MODIFIED) &&
                             strchr(filter, p->status)))
                                diff_q(&outq, p);
                        else
                                diff_free_filepair(p);
                }
        }
        free(q->queue);
        *q = outq;
}

void diffcore_std(struct diff_options *options)
{
        if (options->break_opt != -1)
                diffcore_break(options->break_opt);
        if (options->detect_rename)
                diffcore_rename(options);
        if (options->break_opt != -1)
                diffcore_merge_broken();
        if (options->pickaxe)
                diffcore_pickaxe(options->pickaxe, options->pickaxe_opts);
        if (options->orderfile)
                diffcore_order(options->orderfile);
        diff_resolve_rename_copy();
        diffcore_apply_filter(options->filter);
}


void diffcore_std_no_resolve(struct diff_options *options)
{
        if (options->pickaxe)
                diffcore_pickaxe(options->pickaxe, options->pickaxe_opts);
        if (options->orderfile)
                diffcore_order(options->orderfile);
        diffcore_apply_filter(options->filter);
}

void diff_addremove(struct diff_options *options,
                    int addremove, unsigned mode,
                    const unsigned char *sha1,
                    const char *base, const char *path)
{
        char concatpath[PATH_MAX];
        struct diff_filespec *one, *two;

        /* This may look odd, but it is a preparation for
         * feeding "there are unchanged files which should
         * not produce diffs, but when you are doing copy
         * detection you would need them, so here they are"
         * entries to the diff-core.  They will be prefixed
         * with something like '=' or '*' (I haven't decided
         * which but should not make any difference).
         * Feeding the same new and old to diff_change() 
         * also has the same effect.
         * Before the final output happens, they are pruned after
         * merged into rename/copy pairs as appropriate.
         */
        if (options->reverse_diff)
                addremove = (addremove == '+' ? '-' :
                             addremove == '-' ? '+' : addremove);

        if (!path) path = "";
        sprintf(concatpath, "%s%s", base, path);
        one = alloc_filespec(concatpath);
        two = alloc_filespec(concatpath);

        if (addremove != '+')
                fill_filespec(one, sha1, mode);
        if (addremove != '-')
                fill_filespec(two, sha1, mode);

        diff_queue(&diff_queued_diff, one, two);
}

void diff_change(struct diff_options *options,
                 unsigned old_mode, unsigned new_mode,
                 const unsigned char *old_sha1,
                 const unsigned char *new_sha1,
                 const char *base, const char *path) 
{
        char concatpath[PATH_MAX];
        struct diff_filespec *one, *two;

        if (options->reverse_diff) {
                unsigned tmp;
                const unsigned char *tmp_c;
                tmp = old_mode; old_mode = new_mode; new_mode = tmp;
                tmp_c = old_sha1; old_sha1 = new_sha1; new_sha1 = tmp_c;
        }
        if (!path) path = "";
        sprintf(concatpath, "%s%s", base, path);
        one = alloc_filespec(concatpath);
        two = alloc_filespec(concatpath);
        fill_filespec(one, old_sha1, old_mode);
        fill_filespec(two, new_sha1, new_mode);

        diff_queue(&diff_queued_diff, one, two);
}

void diff_unmerge(struct diff_options *options,
                  const char *path)
{
        struct diff_filespec *one, *two;
        one = alloc_filespec(path);
        two = alloc_filespec(path);
        diff_queue(&diff_queued_diff, one, two);
}