ls-remote & transport API: release "struct transport_ls_refs_options"

Fix a memory leak in codepaths that use the "struct
transport_ls_refs_options" API. Since the introduction of the struct
in 39835409d1 (connect, transport: encapsulate arg in struct,
2021-02-05) the caller has been responsible for freeing it.

That commit in turn migrated code originally added in
402c47d939 (clone: send ref-prefixes when using protocol v2,
2018-07-20) and b4be74105f (ls-remote: pass ref prefixes when
requesting a remote's refs, 2018-03-15). Only some of those codepaths
were releasing the allocated resources of the struct, now all of them
will.

Mark the "t/t5511-refspec.sh" test as passing when git is compiled
with SANITIZE=leak. They'll now be listed as running under the
"GIT_TEST_PASSING_SANITIZE_LEAK=true" test mode (the "linux-leaks" CI
target). Previously 24/47 tests would fail.

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

builtin/clone.c

@@ -1233,7 +1233,8 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	}
 	else {
 		const char *branch;
-		char *ref;
+		const char *ref;
+		char *ref_free = NULL;
 
 		if (option_branch)
 			die(_("Remote branch %s not found in upstream %s"),
@@ -1250,17 +1251,16 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 		    skip_prefix(transport_ls_refs_options.unborn_head_target,
 				"refs/heads/", &branch)) {
 			ref = transport_ls_refs_options.unborn_head_target;
-			transport_ls_refs_options.unborn_head_target = NULL;
 			create_symref("HEAD", ref, reflog_msg.buf);
 		} else {
 			branch = git_default_branch_name(0);
-			ref = xstrfmt("refs/heads/%s", branch);
+			ref_free = xstrfmt("refs/heads/%s", branch);
+			ref = ref_free;
 		}
 
 		if (!option_bare)
 			install_branch_config(0, branch, remote_name, ref);
-
-		free(ref);
+		free(ref_free);
 	}
 
 	write_refspec_config(src_ref_prefix, our_head_points_at,
@@ -1312,7 +1312,6 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	UNLEAK(repo);
 	junk_mode = JUNK_LEAVE_ALL;
 
-	strvec_clear(&transport_ls_refs_options.ref_prefixes);
-	free(transport_ls_refs_options.unborn_head_target);
+	transport_ls_refs_options_release(&transport_ls_refs_options);
 	return err;
 }

builtin/fetch.c

@@ -1593,7 +1593,7 @@ static int do_fetch(struct transport *transport,
 	} else
 		remote_refs = NULL;
 
-	strvec_clear(&transport_ls_refs_options.ref_prefixes);
+	transport_ls_refs_options_release(&transport_ls_refs_options);
 
 	ref_map = get_ref_map(transport->remote, remote_refs, rs,
 			      tags, &autotags);

builtin/ls-remote.c

@@ -155,6 +155,7 @@ int cmd_ls_remote(int argc, const char **argv, const char *prefix)
 
 	ref_array_clear(&ref_array);
 	if (transport_disconnect(transport))
-		return 1;
+		status = 1;
+	transport_ls_refs_options_release(&transport_options);
 	return status;
 }

connect.c

@@ -379,7 +379,7 @@ struct ref **get_remote_heads(struct packet_reader *reader,
 
 /* Returns 1 when a valid ref has been added to `list`, 0 otherwise */
 static int process_ref_v2(struct packet_reader *reader, struct ref ***list,
-			  char **unborn_head_target)
+			  const char **unborn_head_target)
 {
 	int ret = 1;
 	int i = 0;
@@ -483,7 +483,7 @@ struct ref **get_remote_refs(int fd_out, struct packet_reader *reader,
 	const char *hash_name;
 	struct strvec *ref_prefixes = transport_options ?
 		&transport_options->ref_prefixes : NULL;
-	char **unborn_head_target = transport_options ?
+	const char **unborn_head_target = transport_options ?
 		&transport_options->unborn_head_target : NULL;
 	*list = NULL;
 

t/t5511-refspec.sh

@@ -2,6 +2,7 @@
 
 test_description='refspec parsing'
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 test_refspec () {

transport.c

@@ -1292,7 +1292,7 @@ int transport_push(struct repository *r,
 							       &transport_options);
 		trace2_region_leave("transport_push", "get_refs_list", r);
 
-		strvec_clear(&transport_options.ref_prefixes);
+		transport_ls_refs_options_release(&transport_options);
 
 		if (flags & TRANSPORT_PUSH_ALL)
 			match_flags |= MATCH_REFS_ALL;
@@ -1420,6 +1420,12 @@ const struct ref *transport_get_remote_refs(struct transport *transport,
 	return transport->remote_refs;
 }
 
+void transport_ls_refs_options_release(struct transport_ls_refs_options *opts)
+{
+	strvec_clear(&opts->ref_prefixes);
+	free((char *)opts->unborn_head_target);
+}
+
 int transport_fetch_refs(struct transport *transport, struct ref *refs)
 {
 	int rc;

transport.h

@@ -257,15 +257,19 @@ struct transport_ls_refs_options {
 	/*
 	 * If unborn_head_target is not NULL, and the remote reports HEAD as
 	 * pointing to an unborn branch, transport_get_remote_refs() stores the
-	 * unborn branch in unborn_head_target. It should be freed by the
-	 * caller.
+	 * unborn branch in unborn_head_target.
 	 */
-	char *unborn_head_target;
+	const char *unborn_head_target;
 };
 #define TRANSPORT_LS_REFS_OPTIONS_INIT { \
 	.ref_prefixes = STRVEC_INIT, \
 }
 
+/**
+ * Release the "struct transport_ls_refs_options".
+ */
+void transport_ls_refs_options_release(struct transport_ls_refs_options *opts);
+
 /*
  * Retrieve refs from a remote.
  */