X-Git-Url: https://git.verplant.org/?a=blobdiff_plain;f=read-tree.c;h=3746984125026d608493e407c1ef3cc98c007a71;hb=76f38347b4199f65e8c897ebf4f9ce1d3a24378b;hp=59e6950a4c0e38f41274d95ab9d8cdbf6b540b43;hpb=d99082e0e3436f5fcf259aa1a4189473f6bb5ce3;p=git.git

diff --git a/read-tree.c b/read-tree.c
index 59e6950a..37469841 100644
--- a/read-tree.c
+++ b/read-tree.c
@@ -7,147 +7,263 @@
 
 static int stage = 0;
 
-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->ce_mode = htonl(mode);
-	ce->ce_flags = create_ce_flags(baselen + len, stage);
-	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 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;
-			continue;
-		}
-		if (read_one_entry(sha1, base, baselen, path, mode) < 0)
-			return -1;
-	}
-	return 0;
+	ret = read_tree(buffer, size, stage);
+	free(buffer);
+	return ret;
 }
 
-static int remove_lock = 0;
+static char *lockfile_name;
 
 static void remove_lock_file(void)
 {
-	if (remove_lock)
-		unlink(".git/index.lock");
+	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 identical entries and collapses them to state 0.
+ * This removes all trivial merges that don't change the tree
+ * and collapses them to state 0.
  *
- * _Any_ other merge (even a trivial one, like both ) 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.
+ * _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 int same_entry(struct cache_entry *a,
-			struct cache_entry *b,
-			struct cache_entry *c)
+static struct cache_entry *merge_entries(struct cache_entry *a,
+					 struct cache_entry *b,
+					 struct cache_entry *c)
 {
 	int len = ce_namelen(a);
-	return	a->ce_mode == b->ce_mode &&
-		a->ce_mode == c->ce_mode &&
-		ce_namelen(b) == len &&
-		ce_namelen(c) == len &&
-		!memcmp(a->name, b->name, len) &&
-		!memcmp(a->name, c->name, len) &&
-		!memcmp(a->sha1, b->sha1, 20) &&
-		!memcmp(a->sha1, c->sha1, 20);
+
+	/*
+	 * 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;
+}
+
+/*
+ * When a CE gets turned into an unmerged entry, we
+ * want it to be up-to-date
+ */
+static void verify_uptodate(struct cache_entry *ce)
+{
+	struct stat st;
+
+	if (!lstat(ce->name, &st)) {
+		unsigned changed = ce_match_stat(ce, &st);
+		if (!changed)
+			return;
+		errno = 0;
+	}
+	if (errno == ENOENT)
+		return;
+	die("Entry '%s' not uptodate. Cannot merge.", ce->name);
 }
 
+/*
+ * If the old tree contained a CE that isn't even in the
+ * result, that's always a problem, regardless of whether
+ * it's up-to-date or not (ie it can be a file that we
+ * have updated but not committed yet).
+ */
+static void reject_merge(struct cache_entry *ce)
+{
+	die("Entry '%s' would be overwritten by merge. Cannot merge.", ce->name);
+}
+
+#define CHECK_OLD(ce) if (old && same(old, ce)) { verify_uptodate(old); old = NULL; }
+
 static void trivially_merge_cache(struct cache_entry **src, int nr)
 {
 	struct cache_entry **dst = src;
+	struct cache_entry *old = NULL;
 
 	while (nr) {
-		struct cache_entry *ce;
+		struct cache_entry *ce, *result;
 
 		ce = src[0];
-		if (nr > 2 && same_entry(ce, src[1], src[2])) {
+
+		/* We throw away original cache entries except for the stat information */
+		if (!ce_stage(ce)) {
+			if (old)
+				reject_merge(old);
+			old = ce;
+			src++;
+			nr--;
+			active_nr--;
+			continue;
+		}
+		if (old && !path_matches(old, ce))
+			reject_merge(old);
+		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 (old && same(old, result)) {
+				*result = *old;
+				old = NULL;
+			}
+			CHECK_OLD(ce);
+			CHECK_OLD(src[1]);
+			CHECK_OLD(src[2]);
+			ce = result;
 			ce->ce_flags &= ~htons(CE_STAGEMASK);
 			src += 2;
 			nr -= 2;
 			active_nr -= 2;
 		}
-		*dst = ce;
+
+		/*
+		 * If we had an old entry that we now effectively
+		 * overwrite, make sure it wasn't dirty.
+		 */
+		CHECK_OLD(ce);
+		*dst++ = ce;
 		src++;
-		dst++;
 		nr--;
 	}
+	if (old)
+		reject_merge(old);
 }
 
+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();
 
-	newfd = open(".git/index.lock", O_RDWR | O_CREAT | O_EXCL, 0600);
+	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);
-	remove_lock = 1;
+	lockfile_name = lockfile;
 
+	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_hex(arg, sha1) < 0)
-			usage("read-tree [-m] <sha1>");
+		if (get_sha1(arg, sha1) < 0)
+			usage(read_tree_usage);
 		if (stage > 3)
-			usage("can't merge more than two trees");
-		if (read_tree(sha1, "", 0) < 0)
+			usage(read_tree_usage);
+		if (unpack_tree(sha1) < 0)
 			die("failed to unpack tree object %s", arg);
 		stage++;
 	}
-	if (stage == 4)
-		trivially_merge_cache(active_cache, active_nr);
-	if (write_cache(newfd, active_cache, active_nr) ||
-	    rename(".git/index.lock", ".git/index"))
+	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");
-	remove_lock = 0;
+	lockfile_name = NULL;
 	return 0;
 }