git-init-db: set up the full default environment
[gitweb.git] / read-tree.c
index 5784802e945e43612cbc5415681e9e08dc1cf1df..283f4d8577261645d0f5e2d85b7f74f13b848f79 100644 (file)
  */
 #include "cache.h"
 
-static int read_one_entry(unsigned char *sha1, const char *base, int baselen, const char *pathname, unsigned mode)
-{
-       int len = strlen(pathname);
-       unsigned int size = cache_entry_size(baselen + len);
-       struct cache_entry *ce = malloc(size);
-
-       memset(ce, 0, size);
-
-       ce->st_mode = mode;
-       ce->namelen = baselen + len;
-       memcpy(ce->name, base, baselen);
-       memcpy(ce->name + baselen, pathname, len+1);
-       memcpy(ce->sha1, sha1, 20);
-       return add_cache_entry(ce, 1);
-}
+static int stage = 0;
 
-static int read_tree(unsigned char *sha1, const char *base, int baselen)
+static int unpack_tree(unsigned char *sha1)
 {
        void *buffer;
        unsigned long size;
-       char type[20];
+       int ret;
 
-       buffer = read_sha1_file(sha1, type, &size);
+       buffer = read_object_with_reference(sha1, "tree", &size, NULL);
        if (!buffer)
                return -1;
-       if (strcmp(type, "tree"))
-               return -1;
-       while (size) {
-               int len = strlen(buffer)+1;
-               unsigned char *sha1 = buffer + len;
-               char *path = strchr(buffer, ' ')+1;
-               unsigned int mode;
-
-               if (size < len + 20 || sscanf(buffer, "%o", &mode) != 1)
-                       return -1;
-
-               buffer = sha1 + 20;
-               size -= len + 20;
-
-               if (S_ISDIR(mode)) {
-                       int retval;
-                       int pathlen = strlen(path);
-                       char *newbase = malloc(baselen + 1 + pathlen);
-                       memcpy(newbase, base, baselen);
-                       memcpy(newbase + baselen, path, pathlen);
-                       newbase[baselen + pathlen] = '/';
-                       retval = read_tree(sha1, newbase, baselen + pathlen + 1);
-                       free(newbase);
-                       if (retval)
-                               return -1;
+       ret = read_tree(buffer, size, stage);
+       free(buffer);
+       return ret;
+}
+
+static char *lockfile_name;
+
+static void remove_lock_file(void)
+{
+       if (lockfile_name)
+               unlink(lockfile_name);
+}
+
+static int path_matches(struct cache_entry *a, struct cache_entry *b)
+{
+       int len = ce_namelen(a);
+       return ce_namelen(b) == len &&
+               !memcmp(a->name, b->name, len);
+}
+
+static int same(struct cache_entry *a, struct cache_entry *b)
+{
+       return a->ce_mode == b->ce_mode && 
+               !memcmp(a->sha1, b->sha1, 20);
+}
+
+
+/*
+ * This removes all trivial merges that don't change the tree
+ * and collapses them to state 0.
+ *
+ * _Any_ other merge is left to user policy.  That includes "both
+ * created the same file", and "both removed the same file" - which are
+ * trivial, but the user might still want to _note_ it. 
+ */
+static struct cache_entry *merge_entries(struct cache_entry *a,
+                                        struct cache_entry *b,
+                                        struct cache_entry *c)
+{
+       int len = ce_namelen(a);
+
+       /*
+        * Are they all the same filename? We won't do
+        * any name merging
+        */
+       if (ce_namelen(b) != len ||
+           ce_namelen(c) != len ||
+           memcmp(a->name, b->name, len) ||
+           memcmp(a->name, c->name, len))
+               return NULL;
+
+       /*
+        * Ok, all three entries describe the same
+        * filename, but maybe the contents or file
+        * mode have changed?
+        *
+        * The trivial cases end up being the ones where two
+        * out of three files are the same:
+        *  - both destinations the same, trivially take either
+        *  - one of the destination versions hasn't changed,
+        *    take the other.
+        *
+        * The "all entries exactly the same" case falls out as
+        * a special case of any of the "two same" cases.
+        *
+        * Here "a" is "original", and "b" and "c" are the two
+        * trees we are merging.
+        */
+       if (same(b,c))
+               return c;
+       if (same(a,b))
+               return c;
+       if (same(a,c))
+               return b;
+       return NULL;
+}
+
+static void trivially_merge_cache(struct cache_entry **src, int nr)
+{
+       static struct cache_entry null_entry;
+       struct cache_entry **dst = src;
+       struct cache_entry *old = &null_entry;
+
+       while (nr) {
+               struct cache_entry *ce, *result;
+
+               ce = src[0];
+
+               /* We throw away original cache entries except for the stat information */
+               if (!ce_stage(ce)) {
+                       old = ce;
+                       src++;
+                       nr--;
+                       active_nr--;
                        continue;
                }
-               if (read_one_entry(sha1, base, baselen, path, mode) < 0)
-                       return -1;
+               if (nr > 2 && (result = merge_entries(ce, src[1], src[2])) != NULL) {
+                       /*
+                        * See if we can re-use the old CE directly?
+                        * That way we get the uptodate stat info.
+                        */
+                       if (path_matches(result, old) && same(result, old))
+                               *result = *old;
+                       ce = result;
+                       ce->ce_flags &= ~htons(CE_STAGEMASK);
+                       src += 2;
+                       nr -= 2;
+                       active_nr -= 2;
+               }
+               *dst++ = ce;
+               src++;
+               nr--;
        }
-       return 0;
 }
 
+static void merge_stat_info(struct cache_entry **src, int nr)
+{
+       static struct cache_entry null_entry;
+       struct cache_entry **dst = src;
+       struct cache_entry *old = &null_entry;
+
+       while (nr) {
+               struct cache_entry *ce;
+
+               ce = src[0];
+
+               /* We throw away original cache entries except for the stat information */
+               if (!ce_stage(ce)) {
+                       old = ce;
+                       src++;
+                       nr--;
+                       active_nr--;
+                       continue;
+               }
+               if (path_matches(ce, old) && same(ce, old))
+                       *ce = *old;
+               ce->ce_flags &= ~htons(CE_STAGEMASK);
+               *dst++ = ce;
+               src++;
+               nr--;
+       }
+}
+
+static char *read_tree_usage = "git-read-tree (<sha> | -m <sha1> [<sha2> <sha3>])";
+
 int main(int argc, char **argv)
 {
-       int i, newfd;
+       int i, newfd, merge;
        unsigned char sha1[20];
+       static char lockfile[MAXPATHLEN+1];
+       const char *indexfile = get_index_file();
+
+       snprintf(lockfile, sizeof(lockfile), "%s.lock", indexfile);
 
-       newfd = open(".dircache/index.lock", O_RDWR | O_CREAT | O_EXCL, 0600);
+       newfd = open(lockfile, O_RDWR | O_CREAT | O_EXCL, 0600);
        if (newfd < 0)
-               usage("unable to create new cachefile");
+               die("unable to create new cachefile");
+       atexit(remove_lock_file);
+       lockfile_name = lockfile;
 
+       merge = 0;
        for (i = 1; i < argc; i++) {
                const char *arg = argv[i];
 
-               /* "-m" stands for "merge" current directory cache */
+               /* "-m" stands for "merge", meaning we start in stage 1 */
                if (!strcmp(arg, "-m")) {
-                       if (active_cache) {
-                               fprintf(stderr, "read-tree: cannot merge old cache on top of new\n");
-                               goto out;
-                       }
-                       if (read_cache() < 0) {
-                               fprintf(stderr, "read-tree: corrupt directory cache\n");
-                               goto out;
+                       int i;
+                       if (stage)
+                               die("-m needs to come first");
+                       read_cache();
+                       for (i = 0; i < active_nr; i++) {
+                               if (ce_stage(active_cache[i]))
+                                       die("you need to resolve your current index first");
                        }
+                       stage = 1;
+                       merge = 1;
                        continue;
                }
-               if (get_sha1_hex(arg, sha1) < 0) {
-                       fprintf(stderr, "read-tree [-m] <sha1>\n");
-                       goto out;
-               }
-               if (read_tree(sha1, "", 0) < 0) {
-                       fprintf(stderr, "failed to unpack tree object %s\n", arg);
-                       goto out;
+               if (get_sha1(arg, sha1) < 0)
+                       usage(read_tree_usage);
+               if (stage > 3)
+                       usage(read_tree_usage);
+               if (unpack_tree(sha1) < 0)
+                       die("failed to unpack tree object %s", arg);
+               stage++;
+       }
+       if (merge) {
+               switch (stage) {
+               case 4: /* Three-way merge */
+                       trivially_merge_cache(active_cache, active_nr);
+                       break;
+               case 2: /* Just read a tree, merge with old cache contents */
+                       merge_stat_info(active_cache, active_nr);
+                       break;
+               default:
+                       die("just how do you expect me to merge %d trees?", stage-1);
                }
        }
-       if (!write_cache(newfd, active_cache, active_nr) && !rename(".dircache/index.lock", ".dircache/index"))
-               return 0;
-
-out:
-       unlink(".dircache/index.lock");
-       exit(1);
+       if (write_cache(newfd, active_cache, active_nr) || rename(lockfile, indexfile))
+               die("unable to write new index file");
+       lockfile_name = NULL;
+       return 0;
 }