Make git-rev-parse support cogito-style "short hex names"

Currently only for unpacked objects, but the infrastructure
is there to do it for packed objects too.

diff --git a/rev-parse.c b/rev-parse.c
index c096dc45ee7606c2b2947400f66c350f5801cb06..95da465f14d2dbe8cd923bf64746e1f0bcab6407 100644 (file)
--- a/rev-parse.c
+++ b/rev-parse.c
@@ -102,13 +102,84 @@ static int get_parent(char *name, unsigned char *result, int idx)
        return -1;
 }
 
+static int find_short_object_filename(int len, const char *name, unsigned char *sha1)
+{
+       static char dirname[PATH_MAX];
+       char hex[40];
+       DIR *dir;
+       int found;
+
+       snprintf(dirname, sizeof(dirname), "%s/%.2s", get_object_directory(), name);
+       dir = opendir(dirname);
+       sprintf(hex, "%.2s", name);
+       found = 0;
+       if (dir) {
+               struct dirent *de;
+               while ((de = readdir(dir)) != NULL) {
+                       if (strlen(de->d_name) != 38)
+                               continue;
+                       if (memcmp(de->d_name, name + 2, len-2))
+                               continue;
+                       memcpy(hex + 2, de->d_name, 38);
+                       if (++found > 1)
+                               break;
+               }
+               closedir(dir);
+       }
+       if (found == 1)
+               return get_sha1_hex(hex, sha1) == 0;
+       return 0;
+}
+
+static int find_short_packed_object(int len, const unsigned char *match, unsigned char *sha1)
+{
+       return 0;
+}
+
+static int get_short_sha1(char *name, unsigned char *sha1)
+{
+       int i;
+       char canonical[40];
+       unsigned char res[20];
+
+       memset(res, 0, 20);
+       memset(canonical, 'x', 40);
+       for (i = 0;;i++) {
+               unsigned char c = name[i];
+               unsigned char val;
+               if (!c || i > 40)
+                       break;
+               if (c >= '0' && c <= '9')
+                       val = c - '0';
+               else if (c >= 'a' && c <= 'f')
+                       val = c - 'a' + 10;
+               else if (c >= 'A' && c <='F') {
+                       val = c - 'A' + 10;
+                       c -= 'A' - 'a';
+               }
+               else
+                       return -1;
+               canonical[i] = c;
+               if (!(i & 1))
+                       val <<= 4;
+               res[i >> 1] |= val;
+       }
+       if (i < 4)
+               return -1;
+       if (find_short_object_filename(i, canonical, sha1))
+               return 0;
+       if (find_short_packed_object(i, res, sha1))
+               return 0;
+       return -1;
+}
+
 /*
  * This is like "get_sha1()", except it allows "sha1 expressions",
  * notably "xyz^" for "parent of xyz"
  */
 static int get_extended_sha1(char *name, unsigned char *sha1)
 {
-       int parent;
+       int parent, ret;
        int len = strlen(name);
 
        parent = 1;
@@ -117,14 +188,16 @@ static int get_extended_sha1(char *name, unsigned char *sha1)
                len--;
        }
        if (len > 1 && name[len-1] == '^') {
-               int ret;
                name[len-1] = 0;
                ret = get_parent(name, sha1, parent);
                name[len-1] = '^';
                if (!ret)
                        return 0;
        }
-       return get_sha1(name, sha1);
+       ret = get_sha1(name, sha1);
+       if (!ret)
+               return 0;
+       return get_short_sha1(name, sha1);
 }
 
 static void show_default(void)