hash-object: fix a trivial leak in --path

Fix a memory leak that happened when the --path option was
provided. This leak has been with us ever since the option was added
in 3970243150 (add --path option to git hash-object, 2008-08-03).

We can now mark "t1007-hash-object.sh" as passing when git is compiled
with SANITIZE=leak. It'll now run in the the
"GIT_TEST_PASSING_SANITIZE_LEAK=true" test mode (the "linux-leaks" CI
target).

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/hash-object.c

@@ -92,6 +92,7 @@ int cmd_hash_object(int argc, const char **argv, const char *prefix)
 	int nongit = 0;
 	unsigned flags = HASH_FORMAT_CHECK;
 	const char *vpath = NULL;
+	char *vpath_free = NULL;
 	const struct option hash_object_options[] = {
 		OPT_STRING('t', NULL, &type, N_("type"), N_("object type")),
 		OPT_BIT('w', NULL, &flags, N_("write the object into the object database"),
@@ -114,8 +115,10 @@ int cmd_hash_object(int argc, const char **argv, const char *prefix)
 	else
 		prefix = setup_git_directory_gently(&nongit);
 
-	if (vpath && prefix)
-		vpath = prefix_filename(prefix, vpath);
+	if (vpath && prefix) {
+		vpath_free = prefix_filename(prefix, vpath);
+		vpath = vpath_free;
+	}
 
 	git_config(git_default_config, NULL);
 
@@ -156,5 +159,7 @@ int cmd_hash_object(int argc, const char **argv, const char *prefix)
 	if (stdin_paths)
 		hash_stdin_paths(type, no_filters, flags, literally);
 
+	free(vpath_free);
+
 	return 0;
 }

t/t1007-hash-object.sh

@@ -2,6 +2,7 @@
 
 test_description="git hash-object"
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 echo_without_newline() {