Merge branch 'tc/merge-default-to-upstream-leakfix'

A memory leak in 'git merge' when run without arguments (which
triggers the default-to-upstream path) has been fixed.  A test has
been added to cover this case.

* tc/merge-default-to-upstream-leakfix:
  merge: fix leak with merge.defaultToUpstream

builtin/merge.c

@@ -1373,7 +1373,7 @@ int cmd_merge(int argc,
 	struct commit_list *common = NULL;
 	const char *best_strategy = NULL, *wt_strategy = NULL;
 	struct commit_list *remoteheads = NULL, *p;
-	void *branch_to_free;
+	void *branch_to_free, *argv_to_free = NULL;
 	int orig_argc = argc;
 	int merge_log_config = -1;
 
@@ -1517,8 +1517,10 @@ int cmd_merge(int argc,
 		option_commit = 1;
 
 	if (!argc) {
-		if (default_to_upstream)
+		if (default_to_upstream) {
 			argc = setup_with_upstream(&argv);
+			argv_to_free = argv;
+		}
 		else
 			die(_("No commit specified and merge.defaultToUpstream not set."));
 	} else if (argc == 1 && !strcmp(argv[0], "-")) {
@@ -1880,6 +1882,7 @@ done:
 	}
 	strbuf_release(&buf);
 	free(branch_to_free);
+	free(argv_to_free);
 	free(pull_twohead);
 	free(pull_octopus);
 	discard_index(the_repository->index);

t/t7600-merge.sh

@@ -1166,4 +1166,21 @@ test_expect_success 'suggested names are not ambiguous' '
 	test_grep remotes/origin/not-local stderr
 '
 
+test_expect_success 'merge with no argument defaults to upstream' '
+	test_when_finished "rm -rf upstream downstream" &&
+	git init upstream &&
+	(
+		cd upstream &&
+		test_commit one &&
+		test_commit two
+	) &&
+	git clone upstream downstream &&
+	(
+		cd downstream &&
+		git reset --hard HEAD^ &&
+		git merge &&
+		test_cmp_rev origin/main HEAD
+	)
+'
+
 test_done