[PATCH] Document git-ssh-pull and git-ssh-push
[gitweb.git] / diff.c
diff --git a/diff.c b/diff.c
index 21771e7756a8b42eeacffabe09a92802b0abd135..046d9a39293fa5d33529b59a251f626785ced233 100644 (file)
--- a/diff.c
+++ b/diff.c
@@ -4,15 +4,15 @@
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <signal.h>
-#include <limits.h>
 #include "cache.h"
 #include "diff.h"
-#include "delta.h"
+#include "diffcore.h"
 
 static const char *diff_opts = "-pu";
 static unsigned char null_sha1[20] = { 0, };
-#define MAX_SCORE 10000
-#define DEFAULT_MINIMUM_SCORE 5000
+
+static int reverse_diff;
+static int use_size_cache;
 
 static const char *external_diff(void)
 {
@@ -77,26 +77,16 @@ static char *sq_expand(const char *src)
 }
 
 static struct diff_tempfile {
-       const char *name;
+       const char *name; /* filename external diff should read from */
        char hex[41];
        char mode[10];
        char tmp_path[50];
 } diff_temp[2];
 
-struct diff_spec {
-       unsigned char blob_sha1[20];
-       unsigned short mode;     /* file mode */
-       unsigned sha1_valid : 1; /* if true, use blob_sha1 and trust mode;
-                                 * if false, use the name and read from
-                                 * the filesystem.
-                                 */
-       unsigned file_valid : 1; /* if false the file does not exist */
-};
-
 static void builtin_diff(const char *name_a,
                         const char *name_b,
                         struct diff_tempfile *temp,
-                        int rename_score)
+                        const char *xfrm_msg)
 {
        int i, next_at, cmd_size;
        const char *diff_cmd = "diff -L'%s%s' -L'%s%s'";
@@ -142,23 +132,24 @@ static void builtin_diff(const char *name_a,
                            diff_arg, input_name_sq[0], input_name_sq[1]);
 
        printf("diff --git a/%s b/%s\n", name_a, name_b);
-       if (!path1[0][0])
+       if (!path1[0][0]) {
                printf("new file mode %s\n", temp[1].mode);
-       else if (!path1[1][0])
+               if (xfrm_msg && xfrm_msg[0])
+                       puts(xfrm_msg);
+       }
+       else if (!path1[1][0]) {
                printf("deleted file mode %s\n", temp[0].mode);
+               if (xfrm_msg && xfrm_msg[0])
+                       puts(xfrm_msg);
+       }
        else {
                if (strcmp(temp[0].mode, temp[1].mode)) {
                        printf("old mode %s\n", temp[0].mode);
                        printf("new mode %s\n", temp[1].mode);
                }
-               if (strcmp(name_a, name_b)) {
-                       if (0 < rename_score)
-                               printf("rename similarity index %d%%\n",
-                                      (int)(0.5+
-                                            rename_score*100.0/MAX_SCORE));
-                       printf("rename old %s\n", name_a);
-                       printf("rename new %s\n", name_b);
-               }
+               if (xfrm_msg && xfrm_msg[0])
+                       puts(xfrm_msg);
+
                if (strncmp(temp[0].mode, temp[1].mode, 3))
                        /* we do not run diff between different kind
                         * of objects.
@@ -169,6 +160,31 @@ static void builtin_diff(const char *name_a,
        execlp("/bin/sh","sh", "-c", cmd, NULL);
 }
 
+struct diff_filespec *alloc_filespec(const char *path)
+{
+       int namelen = strlen(path);
+       struct diff_filespec *spec = xmalloc(sizeof(*spec) + namelen + 1);
+       spec->path = (char *)(spec + 1);
+       strcpy(spec->path, path);
+       spec->should_free = spec->should_munmap = 0;
+       spec->xfrm_flags = 0;
+       spec->size = 0;
+       spec->data = NULL;
+       spec->mode = 0;
+       memset(spec->sha1, 0, 20);
+       return spec;
+}
+
+void fill_filespec(struct diff_filespec *spec, const unsigned char *sha1,
+                  unsigned short mode)
+{
+       if (mode) {
+               spec->mode = DIFF_FILE_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
@@ -201,13 +217,153 @@ static int work_tree_matches(const char *name, const unsigned char *sha1)
                return 0;
        ce = active_cache[pos];
        if ((lstat(name, &st) < 0) ||
-           !S_ISREG(st.st_mode) ||
+           !S_ISREG(st.st_mode) || /* careful! */
            ce_match_stat(ce, &st) ||
            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);
+               s->should_munmap = 1;
+               close(fd);
+       }
+       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_file_size(s->sha1, &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;
+}
+
 static void prep_temp_blob(struct diff_tempfile *temp,
                           void *blob,
                           unsigned long size,
@@ -231,9 +387,9 @@ static void prep_temp_blob(struct diff_tempfile *temp,
 
 static void prepare_temp_file(const char *name,
                              struct diff_tempfile *temp,
-                             struct diff_spec *one)
+                             struct diff_filespec *one)
 {
-       if (!one->file_valid) {
+       if (!DIFF_FILE_VALID(one)) {
        not_a_valid_file:
                /* A '-' entry produces this for file-2, and
                 * a '+' entry produces this for file-1.
@@ -245,13 +401,12 @@ static void prepare_temp_file(const char *name,
        }
 
        if (!one->sha1_valid ||
-           work_tree_matches(name, one->blob_sha1)) {
+           work_tree_matches(name, one->sha1)) {
                struct stat st;
-               temp->name = name;
-               if (lstat(temp->name, &st) < 0) {
+               if (lstat(name, &st) < 0) {
                        if (errno == ENOENT)
                                goto not_a_valid_file;
-                       die("stat(%s): %s", temp->name, strerror(errno));
+                       die("stat(%s): %s", name, strerror(errno));
                }
                if (S_ISLNK(st.st_mode)) {
                        int ret;
@@ -263,31 +418,32 @@ static void prepare_temp_file(const char *name,
                                die("readlink(%s)", name);
                        prep_temp_blob(temp, buf, st.st_size,
                                       (one->sha1_valid ?
-                                       one->blob_sha1 : null_sha1),
+                                       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->blob_sha1));
-                       sprintf(temp->mode, "%06o",
-                               S_IFREG |ce_permissions(st.st_mode));
+                               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 {
-               void *blob;
-               char type[20];
-               unsigned long size;
-
-               blob = read_sha1_file(one->blob_sha1, type, &size);
-               if (!blob || strcmp(type, "blob"))
-                       die("unable to read blob object for %s (%s)",
-                           name, sha1_to_hex(one->blob_sha1));
-               prep_temp_blob(temp, blob, size, one->blob_sha1, one->mode);
-               free(blob);
+               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);
        }
 }
 
@@ -307,52 +463,24 @@ static void remove_tempfile_on_signal(int signo)
        remove_tempfile();
 }
 
-static int detect_rename;
-static int reverse_diff;
-static int diff_raw_output = -1;
-static const char **pathspec;
-static int speccnt;
-static int minimum_score;
-
-static int matches_pathspec(const char *name)
-{
-       int i;
-       int namelen;
-
-       if (speccnt == 0)
-               return 1;
-
-       namelen = strlen(name);
-       for (i = 0; i < speccnt; i++) {
-               int speclen = strlen(pathspec[i]);
-               if (! strncmp(pathspec[i], name, speclen) &&
-                   speclen <= namelen &&
-                   (name[speclen] == 0 || name[speclen] == '/'))
-                       return 1;
-       }
-       return 0;
-}
-
 /* 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 *name,
+static void run_external_diff(const char *pgm,
+                             const char *name,
                              const char *other,
-                             struct diff_spec *one,
-                             struct diff_spec *two,
-                             int rename_score)
+                             struct diff_filespec *one,
+                             struct diff_filespec *two,
+                             const char *xfrm_msg)
 {
        struct diff_tempfile *temp = diff_temp;
        pid_t pid;
        int status;
        static int atexit_asked = 0;
 
-       if (!matches_pathspec(name) && (!other || !matches_pathspec(other)))
-               return;
-
        if (one && two) {
                prepare_temp_file(name, &temp[0], one);
                prepare_temp_file(other ? : name, &temp[1], two);
@@ -370,10 +498,9 @@ static void run_external_diff(const char *name,
        if (pid < 0)
                die("unable to fork");
        if (!pid) {
-               const char *pgm = external_diff();
                if (pgm) {
                        if (one && two) {
-                               const char *exec_arg[9];
+                               const char *exec_arg[10];
                                const char **arg = &exec_arg[0];
                                *arg++ = pgm;
                                *arg++ = name;
@@ -383,8 +510,10 @@ static void run_external_diff(const char *name,
                                *arg++ = temp[1].name;
                                *arg++ = temp[1].hex;
                                *arg++ = temp[1].mode;
-                               if (other)
+                               if (other) {
                                        *arg++ = other;
+                                       *arg++ = xfrm_msg;
+                               }
                                *arg = NULL;
                                execvp(pgm, (char *const*) exec_arg);
                        }
@@ -395,7 +524,7 @@ static void run_external_diff(const char *name,
                 * otherwise we use the built-in one.
                 */
                if (one && two)
-                       builtin_diff(name, other ? : name, temp, rename_score);
+                       builtin_diff(name, other ? : name, temp, xfrm_msg);
                else
                        printf("* Unmerged path %s\n", name);
                exit(0);
@@ -418,335 +547,433 @@ static void run_external_diff(const char *name,
        remove_tempfile();
 }
 
-/*
- * We do not detect circular renames.  Just hold created and deleted
- * entries and later attempt to match them up.  If they do not match,
- * then spit them out as deletes or creates as original.
- */
-
-static struct diff_spec_hold {
-       struct diff_spec_hold *next;
-       struct diff_spec it;
-       unsigned long size;
-       int flags;
-#define MATCHED 1
-#define SHOULD_FREE 2
-#define SHOULD_MUNMAP 4
-       void *data;
-       char path[1];
-} *createdfile, *deletedfile;
-
-static void hold_diff(const char *name,
-                     struct diff_spec *one,
-                     struct diff_spec *two)
+static void run_diff(const char *name,
+                    const char *other,
+                    struct diff_filespec *one,
+                    struct diff_filespec *two,
+                    const char *xfrm_msg)
 {
-       struct diff_spec_hold **list, *elem;
-
-       if (one->file_valid && two->file_valid)
-               die("internal error");
-
-       if (!detect_rename) {
-               run_external_diff(name, NULL, one, two, -1);
-               return;
+       const char *pgm = external_diff();
+       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_external_diff(NULL, name, other, one, null, xfrm_msg);
+               free(null);
+               null = alloc_filespec(one->path);
+               run_external_diff(NULL, name, other, null, two, xfrm_msg);
+               free(null);
        }
-       elem = xmalloc(sizeof(*elem) + strlen(name));
-       strcpy(elem->path, name);
-       elem->size = 0;
-       elem->data = NULL;
-       elem->flags = 0;
-       if (one->file_valid) {
-               list = &deletedfile;
-               elem->it = *one;
+       else
+               run_external_diff(pgm, name, other, one, two, xfrm_msg);
+}
+
+void diff_setup(int flags)
+{
+       if (flags & DIFF_SETUP_REVERSE)
+               reverse_diff = 1;
+       if (flags & 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 oufselves either.
+                        */
+                       read_cache();
        }
-       else {
-               list = &createdfile;
-               elem->it = *two;
+       if (flags & DIFF_SETUP_USE_SIZE_CACHE)
+               use_size_cache = 1;
+       
+}
+
+static int parse_num(const char **cp_p)
+{
+       int num, scale, ch, cnt;
+       const char *cp = *cp_p;
+
+       cnt = num = 0;
+       scale = 1;
+       while ('0' <= (ch = *cp) && ch <= '9') {
+               if (cnt++ < 5) {
+                       /* We simply ignore more than 5 digits precision. */
+                       scale *= 10;
+                       num = num * 10 + ch - '0';
+               }
+               *cp++;
        }
-       elem->next = *list;
-       *list = elem;
+       *cp_p = cp;
+
+       /* user says num divided by scale and we say internally that
+        * is MAX_SCORE * num / scale.
+        */
+       return (MAX_SCORE * num / scale);
 }
 
-static int populate_data(struct diff_spec_hold *s)
+int diff_scoreopt_parse(const char *opt)
 {
-       char type[20];
+       int opt1, opt2, cmd;
 
-       if (s->data)
-               return 0;
-       if (s->it.sha1_valid) {
-               s->data = read_sha1_file(s->it.blob_sha1, type, &s->size);
-               s->flags |= SHOULD_FREE;
-       }
+       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 {
-               struct stat st;
-               int fd;
-               fd = open(s->path, O_RDONLY);
-               if (fd < 0)
-                       return -1;
-               if (fstat(fd, &st)) {
-                       close(fd);
-                       return -1;
+               if (*opt == 0)
+                       opt2 = 0;
+               else if (*opt != '/')
+                       return -1; /* we expect -B80/99 or -B80 */
+               else {
+                       opt++;
+                       opt2 = parse_num(&opt);
                }
-               s->size = st.st_size;
-               s->data = mmap(NULL, s->size, PROT_READ, MAP_PRIVATE, fd, 0);
-               close(fd);
-               if (!s->size)
-                       s->data = "";
-               else
-                       s->flags |= SHOULD_MUNMAP;
        }
-       return 0;
+       if (*opt != 0)
+               return -1;
+       return opt1 | (opt2 << 16);
 }
 
-static void free_data(struct diff_spec_hold *s)
+struct diff_queue_struct diff_queued_diff;
+
+void diff_q(struct diff_queue_struct *queue, struct diff_filepair *dp)
 {
-       if (s->flags & SHOULD_FREE)
-               free(s->data);
-       else if (s->flags & SHOULD_MUNMAP)
-               munmap(s->data, s->size);
-       s->flags &= ~(SHOULD_FREE|SHOULD_MUNMAP);
-       s->data = NULL;
+       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;
 }
 
-static void flush_remaining_diff(struct diff_spec_hold *elem,
-                                int on_created_list)
+struct diff_filepair *diff_queue(struct diff_queue_struct *queue,
+                                struct diff_filespec *one,
+                                struct diff_filespec *two)
 {
-       static struct diff_spec null_file_spec;
+       struct diff_filepair *dp = xmalloc(sizeof(*dp));
+       dp->one = one;
+       dp->two = two;
+       dp->score = 0;
+       dp->source_stays = 0;
+       dp->broken_pair = 0;
+       diff_q(queue, dp);
+       return dp;
+}
 
-       null_file_spec.file_valid = 0;
-       for ( ; elem ; elem = elem->next) {
-               free_data(elem);
-               if (elem->flags & MATCHED)
-                       continue;
-               if (on_created_list)
-                       run_external_diff(elem->path, NULL,
-                                         &null_file_spec, &elem->it, -1);
-               else
-                       run_external_diff(elem->path, NULL,
-                                         &elem->it, &null_file_spec, -1);
-       }
+void diff_free_filepair(struct diff_filepair *p)
+{
+       diff_free_filespec_data(p->one);
+       diff_free_filespec_data(p->two);
+       free(p);
 }
 
-static int is_exact_match(struct diff_spec_hold *src,
-                         struct diff_spec_hold *dst)
+static void diff_flush_raw(struct diff_filepair *p,
+                          int line_termination,
+                          int inter_name_termination)
 {
-       if (src->it.sha1_valid && dst->it.sha1_valid &&
-           !memcmp(src->it.blob_sha1, dst->it.blob_sha1, 20))
-               return 1;
-       if (populate_data(src) || populate_data(dst))
-               /* this is an error but will be caught downstream */
-               return 0;
-       if (src->size == dst->size &&
-           !memcmp(src->data, dst->data, src->size))
-               return 1;
-       return 0;
+       int two_paths;
+       char status[10];
+
+       if (line_termination) {
+               const char *err = "path %s cannot be expressed without -z";
+               if (strchr(p->one->path, line_termination) ||
+                   strchr(p->one->path, inter_name_termination))
+                       die(err, p->one->path);
+               if (strchr(p->two->path, line_termination) ||
+                   strchr(p->two->path, inter_name_termination))
+                       die(err, p->two->path);
+       }
+
+       switch (p->status) {
+       case 'C': case 'R':
+               two_paths = 1;
+               sprintf(status, "%c%03d", p->status,
+                       (int)(0.5 + p->score * 100.0/MAX_SCORE));
+               break;
+       case 'N': case 'D':
+               two_paths = 0;
+               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;
+               }
+               break;
+       default:
+               two_paths = 0;
+               status[0] = p->status;
+               status[1] = 0;
+               break;
+       }
+       printf(":%06o %06o %s ",
+              p->one->mode, p->two->mode, sha1_to_hex(p->one->sha1));
+       printf("%s %s%c%s",
+              sha1_to_hex(p->two->sha1),
+              status,
+              inter_name_termination,
+              p->one->path);
+       if (two_paths)
+               printf("%c%s", inter_name_termination, p->two->path);
+       putchar(line_termination);
 }
 
-static int estimate_similarity(struct diff_spec_hold *src, struct diff_spec_hold *dst)
+int diff_unmodified_pair(struct diff_filepair *p)
 {
-       /* src points at a deleted file and dst points at a created
-        * file.  They may be quite similar, in which case we want to
-        * say src is renamed to dst.
-        *
-        * Compare them and return how similar they are, representing
-        * the score as an integer between 0 and 10000, except
-        * where they match exactly it is considered better than anything
-        * else.
+       /* 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.
         */
-       void *delta;
-       unsigned long delta_size;
-       int score;
+       struct diff_filespec *one, *two;
 
-       delta_size = ((src->size < dst->size) ?
-                     (dst->size - src->size) : (src->size - dst->size));
+       if (DIFF_PAIR_UNMERGED(p))
+               return 0; /* unmerged is interesting */
 
-       /* We would not consider rename followed by more than
-        * minimum_score/MAX_SCORE edits; that is, delta_size must be smaller
-        * than (src->size + dst->size)/2 * minimum_score/MAX_SCORE,
-        * which means...
-        */
+       one = p->one;
+       two = p->two;
 
-       if ((src->size+dst->size)*minimum_score < delta_size*MAX_SCORE*2)
+       /* 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;
 
-       delta = diff_delta(src->data, src->size,
-                          dst->data, dst->size,
-                          &delta_size);
-       free(delta);
-
-       /* This "delta" is really xdiff with adler32 and all the
-        * overheads but it is a quick and dirty approximation.
-        *
-        * Now we will give some score to it.  100% edit gets
-        * 0 points and 0% edit gets MAX_SCORE points.  That is, every
-        * 1/MAX_SCORE edit gets 1 point penalty.  The amount of penalty is:
-        *
-        * (delta_size * 2 / (src->size + dst->size)) * MAX_SCORE
-        *
+       /* both are valid and point at the same path.  that is, we are
+        * dealing with a change.
         */
-       score = MAX_SCORE-(MAX_SCORE*2*delta_size/(src->size+dst->size));
-       if (score < 0) return 0;
-       if (MAX_SCORE < score) return MAX_SCORE;
-       return score;
+       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;
 }
 
-struct diff_score {
-       struct diff_spec_hold *src;
-       struct diff_spec_hold *dst;
-       int score;
-};
-
-static int score_compare(const void *a_, const void *b_)
+static void diff_flush_patch(struct diff_filepair *p)
 {
-       const struct diff_score *a = a_, *b = b_;
-       return b->score - a->score;
+       const char *name, *other;
+       char msg_[PATH_MAX*2+200], *msg;
+
+       if (diff_unmodified_pair(p))
+               return;
+
+       name = p->one->path;
+       other = (strcmp(name, p->two->path) ? p->two->path : NULL);
+       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 */ 
+
+       switch (p->status) {
+       case 'C':
+               sprintf(msg_,
+                       "similarity index %d%%\n"
+                       "copy from %s\n"
+                       "copy to %s",
+                       (int)(0.5 + p->score * 100.0/MAX_SCORE),
+                       p->one->path, p->two->path);
+               msg = msg_;
+               break;
+       case 'R':
+               sprintf(msg_,
+                       "similarity index %d%%\n"
+                       "rename from %s\n"
+                       "rename to %s",
+                       (int)(0.5 + p->score * 100.0/MAX_SCORE),
+                       p->one->path, p->two->path);
+               msg = msg_;
+               break;
+       case 'D': case 'N':
+               if (DIFF_PAIR_BROKEN(p)) {
+                       sprintf(msg_,
+                               "dissimilarity index %d%%",
+                               (int)(0.5 + p->score * 100.0/MAX_SCORE));
+                       msg = msg_;
+               }
+               else
+                       msg = NULL;
+               break;
+       default:
+               msg = NULL;
+       }
+
+       if (DIFF_PAIR_UNMERGED(p))
+               run_diff(name, NULL, NULL, NULL, NULL);
+       else
+               run_diff(name, other, p->one, p->two, msg);
 }
 
-static void flush_rename_pair(struct diff_spec_hold *src,
-                             struct diff_spec_hold *dst,
-                             int rename_score)
+int diff_queue_is_empty(void)
 {
-       src->flags |= MATCHED;
-       dst->flags |= MATCHED;
-       free_data(src);
-       free_data(dst);
-       run_external_diff(src->path, dst->path,
-                         &src->it, &dst->it, rename_score);
+       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;
 }
 
-static void free_held_diff(struct diff_spec_hold *list)
+#if DIFF_DEBUG
+void diff_debug_filespec(struct diff_filespec *s, int x, const char *one)
 {
-       struct diff_spec_hold *h;
-       for (h = list; list; list = h) {
-               h = list->next;
-               free_data(list);
-               free(list);
-       }
+       fprintf(stderr, "queue[%d] %s (%s) %s %06o %s\n",
+               x, 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 ? : "",
+               s->size, s->xfrm_flags);
 }
 
-void diff_flush(void)
+void diff_debug_filepair(const struct diff_filepair *p, int i)
 {
-       int num_create, num_delete, c, d;
-       struct diff_spec_hold *elem, *src, *dst;
-       struct diff_score *mx;
+       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->source_stays, p->broken_pair);
+}
 
-       /* We really want to cull the candidates list early
-        * with cheap tests in order to avoid doing deltas.
-        *
-        * With the current callers, we should not have already
-        * matched entries at this point, but it is nonetheless
-        * checked for sanity.
-        */
-       for (dst = createdfile; dst; dst = dst->next) {
-               if (dst->flags & MATCHED)
-                       continue;
-               for (src = deletedfile; src; src = src->next) {
-                       if (src->flags & MATCHED)
-                               continue;
-                       if (! is_exact_match(src, dst))
-                               continue;
-                       flush_rename_pair(src, dst, MAX_SCORE);
-                       break;
-               }
+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
 
-       /* Count surviving candidates */
-       for (num_create = 0, elem = createdfile; elem; elem = elem->next)
-               if (!(elem->flags & MATCHED))
-                       num_create++;
-
-       for (num_delete = 0, elem = deletedfile; elem; elem = elem->next)
-               if (!(elem->flags & MATCHED))
-                       num_delete++;
-
-       if (num_create == 0 ||  num_delete == 0)
-               goto exit_path;
-
-       mx = xmalloc(sizeof(*mx) * num_create * num_delete);
-       for (c = 0, dst = createdfile; dst; dst = dst->next) {
-               int base = c * num_delete;
-               if (dst->flags & MATCHED)
-                       continue;
-               for (d = 0, src = deletedfile; src; src = src->next) {
-                       struct diff_score *m = &mx[base+d];
-                       if (src->flags & MATCHED)
+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 = 'U';
+               else if (!DIFF_FILE_VALID(p->one))
+                       p->status = 'N';
+               else if (!DIFF_FILE_VALID(p->two))
+                       p->status = 'D';
+               else if (DIFF_PAIR_TYPE_CHANGED(p))
+                       p->status = 'T';
+
+               /* 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 = 'C';
                                continue;
-                       m->src = src;
-                       m->dst = dst;
-                       m->score = estimate_similarity(src, dst);
-                       d++;
+                       }
+                       /* See if there is some other filepair that
+                        * copies from the same source as us.  If so
+                        * we are a copy.  Otherwise we are a rename.
+                        */
+                       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 = 'C';
+                               break;
+                       }
+                       if (!p->status)
+                               p->status = 'R';
+               }
+               else if (memcmp(p->one->sha1, p->two->sha1, 20) ||
+                        p->one->mode != p->two->mode)
+                       p->status = 'M';
+               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 = 'X';
                }
-               c++;
-       }
-       qsort(mx, num_create*num_delete, sizeof(*mx), score_compare);
-
-#if 0
-       for (c = 0; c < num_create * num_delete; c++) {
-               src = mx[c].src;
-               dst = mx[c].dst;
-               if ((src->flags & MATCHED) || (dst->flags & MATCHED))
-                       continue;
-               fprintf(stderr,
-                       "**score ** %d %s %s\n",
-                       mx[c].score, src->path, dst->path);
        }
-#endif
+       diff_debug_queue("resolve-rename-copy done", q);
+}
 
-       for (c = 0; c < num_create * num_delete; c++) {
-               src = mx[c].src;
-               dst = mx[c].dst;
-               if ((src->flags & MATCHED) || (dst->flags & MATCHED))
+void diff_flush(int diff_output_style, int resolve_rename_copy)
+{
+       struct diff_queue_struct *q = &diff_queued_diff;
+       int i;
+       int line_termination = '\n';
+       int inter_name_termination = '\t';
+
+       if (diff_output_style == DIFF_FORMAT_MACHINE)
+               line_termination = inter_name_termination = 0;
+       if (resolve_rename_copy)
+               diff_resolve_rename_copy();
+
+       for (i = 0; i < q->nr; i++) {
+               struct diff_filepair *p = q->queue[i];
+               if ((diff_output_style == DIFF_FORMAT_NO_OUTPUT) ||
+                   (p->status == 'X'))
                        continue;
-               if (mx[c].score < minimum_score)
+               if (p->status == 0)
+                       die("internal error in diff-resolve-rename-copy");
+               switch (diff_output_style) {
+               case DIFF_FORMAT_PATCH:
+                       diff_flush_patch(p);
+                       break;
+               case DIFF_FORMAT_HUMAN:
+               case DIFF_FORMAT_MACHINE:
+                       diff_flush_raw(p, line_termination,
+                                      inter_name_termination);
                        break;
-               flush_rename_pair(src, dst, mx[c].score);
+               }
        }
-       free(mx);
-
- exit_path:
-       flush_remaining_diff(createdfile, 1);
-       flush_remaining_diff(deletedfile, 0);
-       free_held_diff(createdfile);
-       free_held_diff(deletedfile);
-       createdfile = deletedfile = NULL;
-}
-
-int diff_scoreopt_parse(const char *opt)
-{
-       int diglen, num, scale, i;
-       if (opt[0] != '-' || opt[1] != 'M')
-               return -1; /* that is not -M option */
-       diglen = strspn(opt+2, "0123456789");
-       if (diglen == 0 || strlen(opt+2) != diglen)
-               return 0; /* use default */
-       sscanf(opt+2, "%d", &num);
-       for (i = 0, scale = 1; i < diglen; i++)
-               scale *= 10;
-
-       /* user says num divided by scale and we say internally that
-        * is MAX_SCORE * num / scale.
-        */
-       return MAX_SCORE * num / scale;
+       for (i = 0; i < q->nr; i++)
+               diff_free_filepair(q->queue[i]);
+       free(q->queue);
+       q->queue = NULL;
+       q->nr = q->alloc = 0;
 }
 
-void diff_setup(int detect_rename_, int minimum_score_, int reverse_diff_,
-               int diff_raw_output_,
-               const char **pathspec_, int speccnt_)
+void diffcore_std(const char **paths,
+                 int detect_rename, int rename_score,
+                 const char *pickaxe, int pickaxe_opts,
+                 int break_opt,
+                 const char *orderfile)
 {
-       free_held_diff(createdfile);
-       free_held_diff(deletedfile);
-       createdfile = deletedfile = NULL;
-
-       detect_rename = detect_rename_;
-       reverse_diff = reverse_diff_;
-       pathspec = pathspec_;
-       diff_raw_output = diff_raw_output_;
-       speccnt = speccnt_;
-       minimum_score = minimum_score_ ? : DEFAULT_MINIMUM_SCORE;
-}
-
-static const char *git_object_type(unsigned mode)
-{
-       return S_ISDIR(mode) ? "tree" : "blob";
+       if (paths && paths[0])
+               diffcore_pathspec(paths);
+       if (break_opt != -1)
+               diffcore_break(break_opt);
+       if (detect_rename)
+               diffcore_rename(detect_rename, rename_score);
+       if (break_opt != -1)
+               diffcore_merge_broken();
+       if (pickaxe)
+               diffcore_pickaxe(pickaxe, pickaxe_opts);
+       if (orderfile)
+               diffcore_order(orderfile);
 }
 
 void diff_addremove(int addremove, unsigned mode,
@@ -754,49 +981,67 @@ void diff_addremove(int addremove, unsigned mode,
                    const char *base, const char *path)
 {
        char concatpath[PATH_MAX];
-       struct diff_spec spec[2], *one, *two;
-
+       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 (reverse_diff)
-               addremove = (addremove == '+' ? '-' : '+');
-
-       if (0 <= diff_raw_output) {
-               if (!path)
-                       path = "";
-               printf("%c%06o %s %s %s%s%c",
-                      addremove,
-                      mode,
-                      git_object_type(mode), sha1_to_hex(sha1),
-                      base, path, diff_raw_output);
-               return;
-       }
-       if (S_ISDIR(mode))
-               return;
+               addremove = (addremove == '+' ? '-' :
+                            addremove == '-' ? '+' : addremove);
 
-       memcpy(spec[0].blob_sha1, sha1, 20);
-       spec[0].mode = mode;
-       spec[0].sha1_valid = !!memcmp(sha1, null_sha1, 20);
-       spec[0].file_valid = 1;
-       spec[1].file_valid = 0;
+       if (!path) path = "";
+       sprintf(concatpath, "%s%s", base, path);
+       one = alloc_filespec(concatpath);
+       two = alloc_filespec(concatpath);
 
-       if (addremove == '+') {
-               one = spec + 1; two = spec;
-       } else {
-               one = spec; two = one + 1;
-       }
+       if (addremove != '+')
+               fill_filespec(one, sha1, mode);
+       if (addremove != '-')
+               fill_filespec(two, sha1, mode);
 
-       if (path) {
-               strcpy(concatpath, base);
-               strcat(concatpath, path);
-       }
-       hold_diff(path ? concatpath : base, one, two);
+       diff_queue(&diff_queued_diff, one, two);
+}
+
+void diff_helper_input(unsigned old_mode,
+                      unsigned new_mode,
+                      const unsigned char *old_sha1,
+                      const unsigned char *new_sha1,
+                      const char *old_path,
+                      int status,
+                      int score,
+                      const char *new_path)
+{
+       struct diff_filespec *one, *two;
+       struct diff_filepair *dp;
+
+       one = alloc_filespec(old_path);
+       two = alloc_filespec(new_path);
+       if (old_mode)
+               fill_filespec(one, old_sha1, old_mode);
+       if (new_mode)
+               fill_filespec(two, new_sha1, new_mode);
+       dp = diff_queue(&diff_queued_diff, one, two);
+       dp->score = score * MAX_SCORE / 100;
+       dp->status = status;
 }
 
 void diff_change(unsigned old_mode, unsigned new_mode,
                 const unsigned char *old_sha1,
                 const unsigned char *new_sha1,
-                const char *base, const char *path) {
+                const char *base, const char *path) 
+{
        char concatpath[PATH_MAX];
-       struct diff_spec spec[2];
+       struct diff_filespec *one, *two;
 
        if (reverse_diff) {
                unsigned tmp;
@@ -804,48 +1049,20 @@ void diff_change(unsigned old_mode, unsigned new_mode,
                tmp = old_mode; old_mode = new_mode; new_mode = tmp;
                tmp_c = old_sha1; old_sha1 = new_sha1; new_sha1 = tmp_c;
        }
-
-       if (0 <= diff_raw_output) {
-               char old_hex[41];
-               strcpy(old_hex, sha1_to_hex(old_sha1));
-
-               if (!path)
-                       path = "";
-               printf("*%06o->%06o %s %s->%s %s%s%c",
-                      old_mode, new_mode,
-                      git_object_type(new_mode),
-                      old_hex, sha1_to_hex(new_sha1),
-                      base, path, diff_raw_output);
-               return;
-       }
-       if (S_ISDIR(new_mode))
-               return;
-
-       if (path) {
-               strcpy(concatpath, base);
-               strcat(concatpath, path);
-       }
-
-       memcpy(spec[0].blob_sha1, old_sha1, 20);
-       spec[0].mode = old_mode;
-       memcpy(spec[1].blob_sha1, new_sha1, 20);
-       spec[1].mode = new_mode;
-       spec[0].sha1_valid = !!memcmp(old_sha1, null_sha1, 20);
-       spec[1].sha1_valid = !!memcmp(new_sha1, null_sha1, 20);
-       spec[1].file_valid = spec[0].file_valid = 1;
-
-       /* We do not look at changed files as candidate for
-        * rename detection ever.
-        */
-       run_external_diff(path ? concatpath : base, NULL,
-                         &spec[0], &spec[1], -1);
+       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(const char *path)
 {
-       if (0 <= diff_raw_output) {
-               printf("U %s%c", path, diff_raw_output);
-               return;
-       }
-       run_external_diff(path, NULL, NULL, NULL, -1);
+       struct diff_filespec *one, *two;
+       one = alloc_filespec(path);
+       two = alloc_filespec(path);
+       diff_queue(&diff_queued_diff, one, two);
 }