merge: add missing strbuf_release()

We strbuf_reset() this "struct strbuf" in a loop earlier, but never
freed it. Plugs a memory leak that's been here ever since this code
got introduced in 1c7b76b (Build in merge, 2008-07-07).

This takes us from 68 failed tests in "t7600-merge.sh" to 59 under
SANITIZE=leak, and makes "t7604-merge-custom-message.sh" pass!

Signed-off-by: Ævar Arnfjörð Bjarmason <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: avar

builtin/merge.c

@@ -1576,6 +1576,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 
 		finish(head_commit, remoteheads, &commit->object.oid, msg.buf);
 		remove_merge_branch_state(the_repository);
+		strbuf_release(&msg);
 		goto done;
 	} else if (!remoteheads->next && common->next)
 		;
@@ -1746,6 +1747,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		ret = suggest_conflicts();
 
 done:
+	strbuf_release(&buf);
 	free(branch_to_free);
 	return ret;
 }

t/t7604-merge-custom-message.sh

@@ -4,6 +4,7 @@ test_description='git merge
 
 Testing merge when using a custom message for the merge commit.'
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 create_merge_msgs() {