X-Git-Url: https://git.verplant.org/?a=blobdiff_plain;f=read-tree.c;h=46747b5e99b102ed547e87f55a8ee734c9ddb074;hb=7fa6b4e7692926d2d07adee1ef8e277157929058;hp=6862d1012681cd6812ab9bfe1a866446f92a7c91;hpb=f768846e34997fb847c9b875615867d4716d632f;p=git.git

diff --git a/read-tree.c b/read-tree.c
index 6862d101..46747b5e 100644
--- a/read-tree.c
+++ b/read-tree.c
@@ -5,6 +5,8 @@
  */
 #include "cache.h"
 
+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);
@@ -13,12 +15,12 @@ static int read_one_entry(unsigned char *sha1, const char *base, int baselen, co
 
 	memset(ce, 0, size);
 
-	ce->st_mode = mode;
-	ce->namelen = baselen + len;
+	ce->ce_mode = create_ce_mode(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);
+	return add_cache_entry(ce, 1);
 }
 
 static int read_tree(unsigned char *sha1, const char *base, int baselen)
@@ -63,43 +65,196 @@ static int read_tree(unsigned char *sha1, const char *base, int baselen)
 	return 0;
 }
 
+static int remove_lock = 0;
+
+static void remove_lock_file(void)
+{
+	if (remove_lock)
+		unlink(".git/index.lock");
+}
+
+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 (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--;
+	}
+}
+
+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--;
+	}
+}
+
 int main(int argc, char **argv)
 {
-	int i, newfd;
+	int i, newfd, merge;
 	unsigned char sha1[20];
 
-	newfd = open(".dircache/index.lock", O_RDWR | O_CREAT | O_EXCL, 0600);
+	newfd = open(".git/index.lock", 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);
+	remove_lock = 1;
 
+	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)
+				usage("-m needs to come first");
+			read_cache();
+			for (i = 0; i < active_nr; i++) {
+				if (ce_stage(active_cache[i]))
+					usage("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_hex(arg, sha1) < 0)
+			usage("read-tree [-m] <sha1>");
+		if (stage > 3)
+			usage("can't merge more than two trees");
+		if (read_tree(sha1, "", 0) < 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(".git/index.lock", ".git/index"))
+		die("unable to write new index file");
+	remove_lock = 0;
+	return 0;
 }