git-init-db: set up the full default environment
[gitweb.git] / read-tree.c
index 3785e259756b4b1f396baabcff07a9bcb6f75ddc..283f4d8577261645d0f5e2d85b7f74f13b848f79 100644 (file)
  */
 #include "cache.h"
 
-static void create_directories(const char *path)
+static int stage = 0;
+
+static int unpack_tree(unsigned char *sha1)
 {
-       int len = strlen(path);
-       char *buf = malloc(len + 1);
-       const char *slash = path;
-
-       while ((slash = strchr(slash+1, '/')) != NULL) {
-               len = slash - path;
-               memcpy(buf, path, len);
-               buf[len] = 0;
-               mkdir(buf, 0700);
-       }
+       void *buffer;
+       unsigned long size;
+       int ret;
+
+       buffer = read_object_with_reference(sha1, "tree", &size, NULL);
+       if (!buffer)
+               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 int create_file(const char *path)
+static void trivially_merge_cache(struct cache_entry **src, int nr)
 {
-       int fd = open(path, O_WRONLY | O_TRUNC | O_CREAT, 0600);
-       if (fd < 0) {
-               if (errno == ENOENT) {
-                       create_directories(path);
-                       fd = open(path, O_WRONLY | O_TRUNC | O_CREAT, 0600);
+       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 (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 fd;
 }
 
-static int unpack(unsigned char *sha1)
+static void merge_stat_info(struct cache_entry **src, int nr)
 {
-       void *buffer;
-       unsigned long size;
-       char type[20];
+       static struct cache_entry null_entry;
+       struct cache_entry **dst = src;
+       struct cache_entry *old = &null_entry;
 
-       buffer = read_sha1_file(sha1, type, &size);
-       if (!buffer)
-               usage("unable to read sha1 file");
-       if (strcmp(type, "tree"))
-               usage("expected a 'tree' node");
-       while (size) {
-               int len = strlen(buffer)+1;
-               unsigned char *sha1 = buffer + len;
-               char *path = strchr(buffer, ' ')+1;
-               char *data;
-               unsigned long filesize;
-               unsigned int mode;
-               int fd;
-
-               if (size < len + 20 || sscanf(buffer, "%o", &mode) != 1)
-                       usage("corrupt 'tree' file");
-               buffer = sha1 + 20;
-               size -= len + 20;
-               data = read_sha1_file(sha1, type, &filesize);
-               if (!data || strcmp(type, "blob"))
-                       usage("tree file refers to bad file data");
-               fd = create_file(path);
-               if (fd < 0)
-                       usage("unable to create file");
-               if (write(fd, data, filesize) != filesize)
-                       usage("unable to write file");
-               fchmod(fd, mode);
-               close(fd);
-               free(data);
+       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--;
        }
-       return 0;
 }
 
+static char *read_tree_usage = "git-read-tree (<sha> | -m <sha1> [<sha2> <sha3>])";
+
 int main(int argc, char **argv)
 {
-       int fd;
+       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(lockfile, O_RDWR | O_CREAT | O_EXCL, 0600);
+       if (newfd < 0)
+               die("unable to create new cachefile");
+       atexit(remove_lock_file);
+       lockfile_name = lockfile;
 
-       if (argc != 2)
-               usage("read-tree <key>");
-       if (get_sha1_hex(argv[1], sha1) < 0)
-               usage("read-tree <key>");
-       sha1_file_directory = getenv(DB_ENVIRONMENT);
-       if (!sha1_file_directory)
-               sha1_file_directory = DEFAULT_DB_ENVIRONMENT;
-       if (unpack(sha1) < 0)
-               usage("unpack failed");
+       merge = 0;
+       for (i = 1; i < argc; i++) {
+               const char *arg = argv[i];
+
+               /* "-m" stands for "merge", meaning we start in stage 1 */
+               if (!strcmp(arg, "-m")) {
+                       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(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(lockfile, indexfile))
+               die("unable to write new index file");
+       lockfile_name = NULL;
        return 0;
 }