Merge branch 'rs/pull-signed-tag' into maint

When "git merge-recursive" works on history with many criss-cross
merges in "verbose" mode, the names the command assigns to the
virtual merge bases could have overwritten each other by unintended
reuse of the same piece of memory.

* rs/pull-signed-tag:
  commit: use FLEX_ARRAY in struct merge_remote_desc
  merge-recursive: fix verbose output for multiple base trees
  commit: factor out set_merge_remote_desc()
  commit: use xstrdup() in get_merge_parent()

commit.c

@@ -1576,6 +1576,15 @@ int commit_tree_extended(const char *msg, size_t msg_len,
 	return result;
 }
 
+void set_merge_remote_desc(struct commit *commit,
+			   const char *name, struct object *obj)
+{
+	struct merge_remote_desc *desc;
+	FLEX_ALLOC_STR(desc, name, name);
+	desc->obj = obj;
+	commit->util = desc;
+}
+
 struct commit *get_merge_parent(const char *name)
 {
 	struct object *obj;
@@ -1585,13 +1594,8 @@ struct commit *get_merge_parent(const char *name)
 		return NULL;
 	obj = parse_object(oid.hash);
 	commit = (struct commit *)peel_to_type(name, 0, obj, OBJ_COMMIT);
-	if (commit && !commit->util) {
-		struct merge_remote_desc *desc;
-		desc = xmalloc(sizeof(*desc));
-		desc->obj = obj;
-		desc->name = strdup(name);
-		commit->util = desc;
-	}
+	if (commit && !commit->util)
+		set_merge_remote_desc(commit, name, obj);
 	return commit;
 }
 

commit.h

@@ -356,9 +356,11 @@ extern void for_each_mergetag(each_mergetag_fn fn, struct commit *commit, void *
 
 struct merge_remote_desc {
 	struct object *obj; /* the named object, could be a tag */
-	const char *name;
+	char name[FLEX_ARRAY];
 };
 #define merge_remote_util(commit) ((struct merge_remote_desc *)((commit)->util))
+extern void set_merge_remote_desc(struct commit *commit,
+				  const char *name, struct object *obj);
 
 /*
  * Given "name" from the command line to merge, find the commit object

merge-recursive.c

@@ -42,12 +42,9 @@ static struct tree *shift_tree_object(struct tree *one, struct tree *two,
 static struct commit *make_virtual_commit(struct tree *tree, const char *comment)
 {
 	struct commit *commit = alloc_commit_node();
-	struct merge_remote_desc *desc = xmalloc(sizeof(*desc));
 
-	desc->name = comment;
-	desc->obj = (struct object *)commit;
+	set_merge_remote_desc(commit, comment, (struct object *)commit);
 	commit->tree = tree;
-	commit->util = desc;
 	commit->object.parsed = 1;
 	return commit;
 }

t/t3030-merge-recursive.sh

@@ -660,4 +660,22 @@ test_expect_success 'merging with triple rename across D/F conflict' '
 	git merge other
 '
 
+test_expect_success 'merge-recursive remembers the names of all base trees' '
+	git reset --hard HEAD &&
+
+	# more trees than static slots used by oid_to_hex()
+	for commit in $c0 $c2 $c4 $c5 $c6 $c7
+	do
+		git rev-parse "$commit^{tree}"
+	done >trees &&
+
+	# ignore the return code -- it only fails because the input is weird
+	test_must_fail git -c merge.verbosity=5 merge-recursive $(cat trees) -- $c1 $c3 >out &&
+
+	# merge-recursive prints in reverse order, but we do not care
+	sort <trees >expect &&
+	sed -n "s/^virtual //p" out | sort >actual &&
+	test_cmp expect actual
+'
+
 test_done