X-Git-Url: https://git.octo.it/?a=blobdiff_plain;f=read-tree.c;h=ee7a46c909efbc78c59b49d2147165297158882e;hb=aa16021efcd969a44b480d0964e07d52167517db;hp=1a575eb0d29d298ab714c7455cff5b6eced4de2f;hpb=220a0b527bd6ecd30a9d6dfed22195c95e6f445a;p=git.git

diff --git a/read-tree.c b/read-tree.c
index 1a575eb0..ee7a46c9 100644
--- a/read-tree.c
+++ b/read-tree.c
@@ -22,14 +22,6 @@ static int unpack_tree(unsigned char *sha1)
 	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);
@@ -47,27 +39,11 @@ static int same(struct cache_entry *a, struct cache_entry *b)
 /*
  * 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
@@ -85,12 +61,14 @@ static struct cache_entry *merge_entries(struct cache_entry *a,
 	 * 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;
+	if (a && b && c) {
+		if (same(b,c))
+			return c;
+		if (same(a,b))
+			return c;
+		if (same(a,c))
+			return b;
+	}
 	return NULL;
 }
 
@@ -124,142 +102,134 @@ 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)
+static int merged_entry(struct cache_entry *merge, struct cache_entry *old, struct cache_entry **dst)
 {
-	struct cache_entry **dst = src;
-	struct cache_entry *old = NULL;
-
-	while (nr--) {
-		struct cache_entry *ce, *result;
+	merge->ce_flags |= htons(CE_UPDATE);
+	if (old) {
+		/*
+		 * See if we can re-use the old CE directly?
+		 * That way we get the uptodate stat info.
+		 *
+		 * This also removes the UPDATE flag on
+		 * a match.
+		 */
+		if (same(old, merge)) {
+			*merge = *old;
+		} else {
+			verify_uptodate(old);
+		}
+	}
+	merge->ce_flags &= ~htons(CE_STAGEMASK);
+	*dst++ = merge;
+	return 1;
+}
 
-		ce = *src++;
+static int deleted_entry(struct cache_entry *ce, struct cache_entry *old, struct cache_entry **dst)
+{
+	if (old)
+		verify_uptodate(old);
+	ce->ce_mode = 0;
+	*dst++ = ce;
+	return 1;
+}
 
-		/* We throw away original cache entries except for the stat information */
-		if (!ce_stage(ce)) {
-			if (old)
-				reject_merge(old);
-			old = ce;
-			active_nr--;
-			continue;
-		}
-		if (old && !path_matches(old, ce))
-			reject_merge(old);
-		if (nr > 2 && (result = merge_entries(ce, src[1], src[2])) != NULL) {
-			result->ce_flags |= htons(CE_UPDATE);
-			/*
-			 * See if we can re-use the old CE directly?
-			 * That way we get the uptodate stat info.
-			 *
-			 * This also removes the UPDATE flag on
-			 * a match.
-			 */
-			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;
-		}
+static int threeway_merge(struct cache_entry *stages[4], struct cache_entry **dst)
+{
+	struct cache_entry *old = stages[0];
+	struct cache_entry *a = stages[1], *b = stages[2], *c = stages[3];
+	struct cache_entry *merge;
+	int count;
 
-		/*
-		 * If we had an old entry that we now effectively
-		 * overwrite, make sure it wasn't dirty.
-		 */
-		CHECK_OLD(ce);
-		*dst++ = ce;
+	/*
+	 * If we have an entry in the index cache ("old"), then we want
+	 * to make sure that it matches any entries in stage 2 ("first
+	 * branch", aka "b").
+	 */
+	if (old) {
+		if (!b || !same(old, b))
+			return -1;
 	}
+	merge = merge_entries(a, b, c);
+	if (merge)
+		return merged_entry(merge, old, dst);
 	if (old)
-		reject_merge(old);
+		verify_uptodate(old);
+	count = 0;
+	if (a) { *dst++ = a; count++; }
+	if (b) { *dst++ = b; count++; }
+	if (c) { *dst++ = c; count++; }
+	return count;
 }
 
 /*
  * Two-way merge.
  *
- * The rule is: 
- *  - every current entry has to match the old tree
- *  - if the current entry matches the new tree, we leave it
- *    as-is. Otherwise we require that it be up-to-date.
+ * The rule is to "carry forward" what is in the index without losing
+ * information across a "fast forward", favoring a successful merge
+ * over a merge failure when it makes sense.  For details of the
+ * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
+ *
  */
-static void twoway_merge(struct cache_entry **src, int nr)
+static int twoway_merge(struct cache_entry **src, struct cache_entry **dst)
 {
-	static struct cache_entry null_entry;
-	struct cache_entry *old = NULL, *stat = &null_entry;
-	struct cache_entry **dst = src;
-
-	while (nr--) {
-		struct cache_entry *ce = *src++;
-		int stage = ce_stage(ce);
-
-		switch (stage) {
-		case 0:
-			if (old)
-				reject_merge(old);
-			old = ce;
-			stat = ce;
-			active_nr--;
-			continue;
+	struct cache_entry *current = src[0];
+	struct cache_entry *oldtree = src[1], *newtree = src[2];
 
-		case 1:
-			active_nr--;
-			if (!old)
-				continue;
-			if (!path_matches(old, ce) || !same(old, ce))
-				reject_merge(old);
-			continue;
+	if (src[3])
+		return -1;
 
-		case 2:
-			ce->ce_flags |= htons(CE_UPDATE);
-			if (old) {
-				if (!path_matches(old, ce))
-					reject_merge(old);
-				/*
-				 * This also removes the UPDATE flag on
-				 * a match
-				 */
-				if (same(old, ce))
-					*ce = *old;
-				else
-					verify_uptodate(old);
-				old = NULL;
-			}
-			ce->ce_flags &= ~htons(CE_STAGEMASK);
-			*dst++ = ce;
-			continue;
+	if (current) {
+		if ((!oldtree && !newtree) || /* 4 and 5 */
+		    (!oldtree && newtree &&
+		     same(current, newtree)) || /* 6 and 7 */
+		    (oldtree && newtree &&
+		     same(oldtree, newtree)) || /* 14 and 15 */
+		    (oldtree && newtree &&
+		     !same(oldtree, newtree) && /* 18 and 19*/
+		     same(current, newtree))) {
+			*dst++ = current;
+			return 1;
+		}
+		else if (oldtree && !newtree && same(current, oldtree)) {
+			/* 10 or 11 */
+			return deleted_entry(oldtree, current, dst);
+		}
+		else if (oldtree && newtree &&
+			 same(current, oldtree) && !same(current, newtree)) {
+			/* 20 or 21 */
+			return merged_entry(newtree, current, dst);
 		}
-		die("impossible two-way stage");
+		else
+			/* all other failures */
+			return -1;
 	}
-	if (old)
-		reject_merge(old);
+	else if (newtree)
+		return merged_entry(newtree, current, dst);
+	else
+		return deleted_entry(oldtree, current, dst);
 }
 
-static void merge_stat_info(struct cache_entry **src, int nr)
+/*
+ * One-way merge.
+ *
+ * The rule is:
+ * - take the stat information from stage0, take the data from stage1
+ */
+static int oneway_merge(struct cache_entry **src, struct cache_entry **dst)
 {
-	static struct cache_entry null_entry;
-	struct cache_entry **dst = src;
-	struct cache_entry *stat = &null_entry;
+	struct cache_entry *old = src[0];
+	struct cache_entry *a = src[1];
 
-	while (nr--) {
-		struct cache_entry *ce = *src++;
+	if (src[2] || src[3])
+		return -1;
 
-		/* We throw away original cache entries except for the stat information */
-		if (!ce_stage(ce)) {
-			stat = ce;
-			active_nr--;
-			continue;
-		}
-		if (path_matches(ce, stat) && same(ce, stat))
-			*ce = *stat;
-		ce->ce_flags &= ~htons(CE_STAGEMASK);
-		*dst++ = ce;
+	if (!a)
+		return 0;
+	if (old && same(old, a)) {
+		*dst++ = old;
+		return 1;
 	}
+	return merged_entry(a, NULL, dst);
 }
 
 static void check_updates(struct cache_entry **src, int nr)
@@ -273,6 +243,11 @@ static void check_updates(struct cache_entry **src, int nr)
 	unsigned short mask = htons(CE_UPDATE);
 	while (nr--) {
 		struct cache_entry *ce = *src++;
+		if (!ce->ce_mode) {
+			if (update)
+				unlink(ce->name);
+			continue;
+		}
 		if (ce->ce_flags & mask) {
 			ce->ce_flags &= ~mask;
 			if (update)
@@ -281,24 +256,74 @@ static void check_updates(struct cache_entry **src, int nr)
 	}
 }
 
-static char *read_tree_usage = "git-read-tree (<sha> | -m <sha1> [<sha2> [<sha3>]])";
+typedef int (*merge_fn_t)(struct cache_entry **, struct cache_entry **);
+
+static void merge_cache(struct cache_entry **src, int nr, merge_fn_t fn)
+{
+	struct cache_entry **dst = src;
+
+	while (nr) {
+		int entries;
+		struct cache_entry *name, *ce, *stages[4] = { NULL, };
+
+		name = ce = *src;
+		for (;;) {
+			int stage = ce_stage(ce);
+			stages[stage] = ce;
+			ce = *++src;
+			active_nr--;
+			if (!--nr)
+				break;
+			if (!path_matches(ce, name))
+				break;
+		}
+
+		entries = fn(stages, dst);
+		if (entries < 0)
+			reject_merge(name);
+		dst += entries;
+		active_nr += entries;
+	}
+	check_updates(active_cache, active_nr);
+}
+
+static int read_cache_unmerged(void)
+{
+	int i, deleted;
+	struct cache_entry **dst;
+
+	read_cache();
+	dst = active_cache;
+	deleted = 0;
+	for (i = 0; i < active_nr; i++) {
+		struct cache_entry *ce = active_cache[i];
+		if (ce_stage(ce)) {
+			deleted++;
+			continue;
+		}
+		if (deleted)
+			*dst = ce;
+		dst++;
+	}
+	active_nr -= deleted;
+	return deleted;
+}
+
+static char *read_tree_usage = "git-read-tree (<sha> | -m [-u] <sha1> [<sha2> [<sha3>]])";
+
+static struct cache_file cache_file;
 
 int main(int argc, char **argv)
 {
-	int i, newfd, merge;
+	int i, newfd, merge, reset;
 	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);
+	newfd = hold_index_file_for_update(&cache_file, get_index_file());
 	if (newfd < 0)
 		die("unable to create new cachefile");
-	atexit(remove_lock_file);
-	lockfile_name = lockfile;
 
 	merge = 0;
+	reset = 0;
 	for (i = 1; i < argc; i++) {
 		const char *arg = argv[i];
 
@@ -308,16 +333,22 @@ int main(int argc, char **argv)
 			continue;
 		}
 
+		/* This differs from "-m" in that we'll silently ignore unmerged entries */
+		if (!strcmp(arg, "--reset")) {
+			if (stage || merge)
+				usage(read_tree_usage);
+			reset = 1;
+			merge = 1;
+			stage = 1;
+			read_cache_unmerged();
+		}
+
 		/* "-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");
-			}
+			if (stage || merge)
+				usage(read_tree_usage);
+			if (read_cache_unmerged())
+				die("you need to resolve your current index first");
 			stage = 1;
 			merge = 1;
 			continue;
@@ -330,25 +361,20 @@ int main(int argc, char **argv)
 			die("failed to unpack tree object %s", arg);
 		stage++;
 	}
+	if (update && !merge)
+		usage(read_tree_usage);
 	if (merge) {
-		switch (stage) {
-		case 4:	/* Three-way merge */
-			trivially_merge_cache(active_cache, active_nr);
-			check_updates(active_cache, active_nr);
-			break;
-		case 3:	/* Update from one tree to another */
-			twoway_merge(active_cache, active_nr);
-			check_updates(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:
+		static const merge_fn_t merge_function[] = {
+			[1] = oneway_merge,
+			[2] = twoway_merge,
+			[3] = threeway_merge,
+		};
+		if (stage < 2 || stage > 4)
 			die("just how do you expect me to merge %d trees?", stage-1);
-		}
+		merge_cache(active_cache, active_nr, merge_function[stage-1]);
 	}
-	if (write_cache(newfd, active_cache, active_nr) || rename(lockfile, indexfile))
+	if (write_cache(newfd, active_cache, active_nr) ||
+	    commit_index_file(&cache_file))
 		die("unable to write new index file");
-	lockfile_name = NULL;
 	return 0;
 }