remote: add tests for remote-branch edge cases

Add tests for the case when there are no branches on the remote and when
HEAD is detached but has the id of a non-branch. In both of these cases,
we should return ENOTFOUND.

tests/network/remote/defaultbranch.c

@@ -54,11 +54,40 @@ void test_network_remote_defaultbranch__no_default_branch(void)
 	git_remote *remote_b;
 	const git_remote_head **heads;
 	size_t len;
+	git_buf buf = GIT_BUF_INIT;
 
 	cl_git_pass(git_remote_create(&remote_b, g_repo_b, "self", git_repository_path(g_repo_b)));
 	cl_git_pass(git_remote_connect(remote_b, GIT_DIRECTION_FETCH));
 	cl_git_pass(git_remote_ls(&heads, &len, remote_b));
 	cl_assert_equal_i(0, len);
 
+	cl_git_fail_with(GIT_ENOTFOUND, git_remote_default_branch(&buf, remote_b));
+
 	git_remote_free(remote_b);
 }
+
+void test_network_remote_defaultbranch__detached_sharing_nonbranch_id(void)
+{
+	git_oid id, id_cloned;
+	git_reference *ref;
+	git_buf buf = GIT_BUF_INIT;
+	git_repository *cloned_repo;
+
+	cl_git_pass(git_reference_name_to_id(&id, g_repo_a, "HEAD"));
+	cl_git_pass(git_repository_detach_head(g_repo_a, NULL, NULL));
+	cl_git_pass(git_reference_remove(g_repo_a, "refs/heads/master"));
+	cl_git_pass(git_reference_remove(g_repo_a, "refs/heads/not-good"));
+	cl_git_pass(git_reference_create(&ref, g_repo_a, "refs/foo/bar", &id, 1, NULL, NULL));
+	git_reference_free(ref);
+
+	cl_git_pass(git_remote_connect(g_remote, GIT_DIRECTION_FETCH));
+	cl_git_fail_with(GIT_ENOTFOUND, git_remote_default_branch(&buf, g_remote));
+
+	cl_git_pass(git_clone(&cloned_repo, git_repository_path(g_repo_a), "./local-detached", NULL));
+
+	cl_assert(git_repository_head_detached(cloned_repo));
+	cl_git_pass(git_reference_name_to_id(&id_cloned, g_repo_a, "HEAD"));
+	cl_assert(git_oid_equal(&id, &id_cloned));
+
+	git_repository_free(cloned_repo);
+}