Merge pull request #5770 from libgit2/ethomson/empty_default_branch

Cope with empty default branch

src/remote.c

@@ -1141,6 +1141,16 @@ static int remote_head_for_ref(git_remote_head **out, git_remote *remote, git_re
 		ref_name = git_reference_name(resolved_ref);
 	}
 
+	/*
+	 * The ref name may be unresolvable - perhaps it's pointing to
+	 * something invalid.  In this case, there is no remote head for
+	 * this ref.
+	 */
+	if (!ref_name) {
+		error = 0;
+		goto cleanup;
+	}
+
 	if ((error = ref_to_update(&update, &remote_name, remote, spec, ref_name)) < 0)
 		goto cleanup;
 

src/repository.c

@@ -2092,7 +2092,8 @@ static int repo_init_head(const char *repo_dir, const char *given)
 	if (given) {
 		initial_head = given;
 	} else if ((error = git_config_open_default(&cfg)) >= 0 &&
-	           (error = git_config_get_string_buf(&cfg_branch, cfg, "init.defaultbranch")) >= 0) {
+	           (error = git_config_get_string_buf(&cfg_branch, cfg, "init.defaultbranch")) >= 0 &&
+	           *cfg_branch.ptr) {
 		initial_head = cfg_branch.ptr;
 	}
 

tests/fetchhead/nonetwork.c

@@ -319,6 +319,16 @@ static int assert_master_for_merge(const char *ref, const char *url, const git_o
 	return 0;
 }
 
+static int assert_none_for_merge(const char *ref, const char *url, const git_oid *id, unsigned int is_merge, void *data)
+{
+	GIT_UNUSED(ref);
+	GIT_UNUSED(url);
+	GIT_UNUSED(id);
+	GIT_UNUSED(data);
+
+	return is_merge ? -1 : 0;
+}
+
 void test_fetchhead_nonetwork__unborn_with_upstream(void)
 {
 	git_repository *repo;
@@ -366,6 +376,25 @@ void test_fetchhead_nonetwork__fetch_into_repo_with_symrefs(void)
 	cl_git_sandbox_cleanup();
 }
 
+void test_fetchhead_nonetwork__fetch_into_repo_with_invalid_head(void)
+{
+	git_remote *remote;
+	char *strings[] = { "refs/heads/*:refs/remotes/origin/*" };
+	git_strarray refspecs = { strings, 1 };
+
+	cl_set_cleanup(&cleanup_repository, "./test1");
+	cl_git_pass(git_repository_init(&g_repo, "./test1", 0));
+
+	/* HEAD pointing to nonexistent branch */
+	cl_git_rewritefile("./test1/.git/HEAD", "ref: refs/heads/\n");
+
+	cl_git_pass(git_remote_create_anonymous(&remote, g_repo, cl_fixture("testrepo.git")));
+	cl_git_pass(git_remote_fetch(remote, &refspecs, NULL, NULL));
+	cl_git_pass(git_repository_fetchhead_foreach(g_repo, assert_none_for_merge, NULL));
+
+	git_remote_free(remote);
+}
+
 void test_fetchhead_nonetwork__quote_in_branch_name(void)
 {
 	cl_set_cleanup(&cleanup_repository, "./test1");

tests/repo/init.c

@@ -688,3 +688,19 @@ void test_repo_init__defaultbranch_config(void)
 
 	git_reference_free(head);
 }
+
+void test_repo_init__defaultbranch_config_empty(void)
+{
+	git_reference *head;
+
+	cl_set_cleanup(&cleanup_repository, "repo");
+
+	create_tmp_global_config("tmp_global_path", "init.defaultbranch", "");
+
+	cl_git_pass(git_repository_init(&g_repo, "repo", 0));
+	cl_git_pass(git_reference_lookup(&head, g_repo, "HEAD"));
+
+	cl_assert_equal_s("refs/heads/master", git_reference_symbolic_target(head));
+
+	git_reference_free(head);
+}