thodg/libgit2

diff --git a/include/git2/checkout.h b/include/git2/checkout.h
index f49e875..a086408 100644
--- a/include/git2/checkout.h
+++ b/include/git2/checkout.h
@@ -236,6 +236,8 @@ typedef struct git_checkout_opts {
 	git_strarray paths;
 
 	git_tree *baseline; /** expected content of workdir, defaults to HEAD */
+
+	const char *target_directory; /** alternative checkout path to workdir */
 } git_checkout_opts;
 
 #define GIT_CHECKOUT_OPTS_VERSION 1
diff --git a/src/checkout.c b/src/checkout.c
index 065bb50..8f9ec64 100644
--- a/src/checkout.c
+++ b/src/checkout.c
@@ -858,7 +858,7 @@ static int checkout_submodule(
 		return 0;
 
 	if ((error = git_futils_mkdir(
-			file->path, git_repository_workdir(data->repo),
+			file->path, data->opts.target_directory,
 			data->opts.dir_mode, GIT_MKDIR_PATH)) < 0)
 		return error;
 
@@ -1030,7 +1030,7 @@ static int checkout_deferred_remove(git_repository *repo, const char *path)
 {
 #if 0
 	int error = git_futils_rmdir_r(
-		path, git_repository_workdir(repo), GIT_RMDIR_EMPTY_PARENTS);
+		path, data->opts.target_directory, GIT_RMDIR_EMPTY_PARENTS);
 
 	if (error == GIT_ENOTFOUND) {
 		error = 0;
@@ -1163,7 +1163,8 @@ static int checkout_data_init(
 		return -1;
 	}
 
-	if ((error = git_repository__ensure_not_bare(repo, "checkout")) < 0)
+	if ((!proposed || !proposed->target_directory) &&
+		(error = git_repository__ensure_not_bare(repo, "checkout")) < 0)
 		return error;
 
 	data->repo = repo;
@@ -1176,6 +1177,13 @@ static int checkout_data_init(
 	else
 		memmove(&data->opts, proposed, sizeof(git_checkout_opts));
 
+	if (!data->opts.target_directory)
+		data->opts.target_directory = git_repository_workdir(repo);
+	else if (!git_path_isdir(data->opts.target_directory) &&
+			 (error = git_futils_mkdir(data->opts.target_directory, NULL,
+					GIT_DIR_MODE, GIT_MKDIR_VERIFY_DIR)) < 0)
+		goto cleanup;
+
 	/* refresh config and index content unless NO_REFRESH is given */
 	if ((data->opts.checkout_strategy & GIT_CHECKOUT_NO_REFRESH) == 0) {
 		git_config *cfg;
@@ -1238,7 +1246,8 @@ static int checkout_data_init(
 
 	if ((error = git_vector_init(&data->removes, 0, git__strcmp_cb)) < 0 ||
 		(error = git_pool_init(&data->pool, 1, 0)) < 0 ||
-		(error = git_buf_puts(&data->path, git_repository_workdir(repo))) < 0)
+		(error = git_buf_puts(&data->path, data->opts.target_directory)) < 0 ||
+		(error = git_path_to_dir(&data->path)) < 0)
 		goto cleanup;
 
 	data->workdir_len = git_buf_len(&data->path);
@@ -1286,11 +1295,13 @@ int git_checkout_iterator(
 		GIT_ITERATOR_IGNORE_CASE : GIT_ITERATOR_DONT_IGNORE_CASE;
 
 	if ((error = git_iterator_reset(target, data.pfx, data.pfx)) < 0 ||
-		(error = git_iterator_for_workdir(
-			&workdir, data.repo, iterflags | GIT_ITERATOR_DONT_AUTOEXPAND,
+		(error = git_iterator_for_workdir_ext(
+			&workdir, data.repo, data.opts.target_directory,
+			iterflags | GIT_ITERATOR_DONT_AUTOEXPAND,
 			data.pfx, data.pfx)) < 0 ||
 		(error = git_iterator_for_tree(
-			&baseline, data.opts.baseline, iterflags, data.pfx, data.pfx)) < 0)
+			&baseline, data.opts.baseline,
+			iterflags, data.pfx, data.pfx)) < 0)
 		goto cleanup;
 
 	/* Should not have case insensitivity mismatch */
@@ -1358,8 +1369,19 @@ int git_checkout_index(
 	int error;
 	git_iterator *index_i;
 
-	if ((error = git_repository__ensure_not_bare(repo, "checkout index")) < 0)
-		return error;
+	if (!index && !repo) {
+		giterr_set(GITERR_CHECKOUT,
+			"Must provide either repository or index to checkout");
+		return -1;
+	}
+	if (index && repo && git_index_owner(index) != repo) {
+		giterr_set(GITERR_CHECKOUT,
+			"Index to checkout does not match repository");
+		return -1;
+	}
+
+	if (!repo)
+		repo = git_index_owner(index);
 
 	if (!index && (error = git_repository_index__weakptr(&index, repo)) < 0)
 		return error;
@@ -1383,8 +1405,19 @@ int git_checkout_tree(
 	git_tree *tree = NULL;
 	git_iterator *tree_i = NULL;
 
-	if ((error = git_repository__ensure_not_bare(repo, "checkout tree")) < 0)
-		return error;
+	if (!treeish && !repo) {
+		giterr_set(GITERR_CHECKOUT,
+			"Must provide either repository or tree to checkout");
+		return -1;
+	}
+	if (treeish && repo && git_object_owner(treeish) != repo) {
+		giterr_set(GITERR_CHECKOUT,
+			"Object to checkout does not match repository");
+		return -1;
+	}
+
+	if (!repo)
+		repo = git_object_owner(treeish);
 
 	if (git_object_peel((git_object **)&tree, treeish, GIT_OBJ_TREE) < 0) {
 		giterr_set(
@@ -1409,8 +1442,7 @@ int git_checkout_head(
 	git_tree *head = NULL;
 	git_iterator *head_i = NULL;
 
-	if ((error = git_repository__ensure_not_bare(repo, "checkout head")) < 0)
-		return error;
+	assert(repo);
 
 	if (!(error = checkout_lookup_head_tree(&head, repo)) &&
 		!(error = git_iterator_for_tree(&head_i, head, 0, NULL, NULL)))
diff --git a/src/iterator.c b/src/iterator.c
index 76b0e41..5917f63 100644
--- a/src/iterator.c
+++ b/src/iterator.c
@@ -1321,9 +1321,10 @@ static void workdir_iterator__free(git_iterator *self)
 	git_ignore__free(&wi->ignores);
 }
 
-int git_iterator_for_workdir(
+int git_iterator_for_workdir_ext(
 	git_iterator **out,
 	git_repository *repo,
+	const char *repo_workdir,
 	git_iterator_flag_t flags,
 	const char *start,
 	const char *end)
@@ -1331,8 +1332,11 @@ int git_iterator_for_workdir(
 	int error;
 	workdir_iterator *wi;
 
-	if (git_repository__ensure_not_bare(repo, "scan working directory") < 0)
-		return GIT_EBAREREPO;
+	if (!repo_workdir) {
+		if (git_repository__ensure_not_bare(repo, "scan working directory") < 0)
+			return GIT_EBAREREPO;
+		repo_workdir = git_repository_workdir(repo);
+	}
 
 	/* initialize as an fs iterator then do overrides */
 	wi = git__calloc(1, sizeof(workdir_iterator));
@@ -1352,7 +1356,7 @@ int git_iterator_for_workdir(
 		return error;
 	}
 
-	return fs_iterator__initialize(out, &wi->fi, git_repository_workdir(repo));
+	return fs_iterator__initialize(out, &wi->fi, repo_workdir);
 }
 
 
diff --git a/src/iterator.h b/src/iterator.h
index 493ff4b..ea88fa6 100644
--- a/src/iterator.h
+++ b/src/iterator.h
@@ -79,15 +79,26 @@ extern int git_iterator_for_index(
 	const char *start,
 	const char *end);
 
+extern int git_iterator_for_workdir_ext(
+	git_iterator **out,
+	git_repository *repo,
+	const char *repo_workdir,
+	git_iterator_flag_t flags,
+	const char *start,
+	const char *end);
+
 /* workdir iterators will match the ignore_case value from the index of the
  * repository, unless you override with a non-zero flag value
  */
-extern int git_iterator_for_workdir(
+GIT_INLINE(int) git_iterator_for_workdir(
 	git_iterator **out,
 	git_repository *repo,
 	git_iterator_flag_t flags,
 	const char *start,
-	const char *end);
+	const char *end)
+{
+	return git_iterator_for_workdir_ext(out, repo, NULL, flags, start, end);
+}
 
 /* for filesystem iterators, you have to explicitly pass in the ignore_case
  * behavior that you desire
diff --git a/tests-clar/checkout/index.c b/tests-clar/checkout/index.c
index a3a0f8f..c7500db 100644
--- a/tests-clar/checkout/index.c
+++ b/tests-clar/checkout/index.c
@@ -506,3 +506,102 @@ void test_checkout_index__issue_1397(void)
 
 	check_file_contents("./issue_1397/crlf_file.txt", "first line\r\nsecond line\r\nboth with crlf");
 }
+
+void test_checkout_index__target_directory(void)
+{
+	git_checkout_opts opts = GIT_CHECKOUT_OPTS_INIT;
+	checkout_counts cts;
+	memset(&cts, 0, sizeof(cts));
+
+	opts.checkout_strategy = GIT_CHECKOUT_SAFE_CREATE;
+	opts.target_directory = "alternative";
+	cl_assert(!git_path_isdir("alternative"));
+
+	opts.notify_flags = GIT_CHECKOUT_NOTIFY_ALL;
+	opts.notify_cb = checkout_count_callback;
+	opts.notify_payload = &cts;
+
+	/* create some files that *would* conflict if we were using the wd */
+	cl_git_mkfile("testrepo/README", "I'm in the way!\n");
+	cl_git_mkfile("testrepo/new.txt", "my new file\n");
+
+	cl_git_pass(git_checkout_index(g_repo, NULL, &opts));
+
+	cl_assert_equal_i(0, cts.n_untracked);
+	cl_assert_equal_i(0, cts.n_ignored);
+	cl_assert_equal_i(4, cts.n_updates);
+
+	check_file_contents("./alternative/README", "hey there\n");
+	check_file_contents("./alternative/branch_file.txt", "hi\nbye!\n");
+	check_file_contents("./alternative/new.txt", "my new file\n");
+
+	cl_git_pass(git_futils_rmdir_r(
+		"alternative", NULL, GIT_RMDIR_REMOVE_FILES));
+}
+
+void test_checkout_index__target_directory_from_bare(void)
+{
+	git_checkout_opts opts = GIT_CHECKOUT_OPTS_INIT;
+	git_index *index;
+	git_object *head = NULL;
+	checkout_counts cts;
+	memset(&cts, 0, sizeof(cts));
+
+	test_checkout_index__cleanup();
+
+	g_repo = cl_git_sandbox_init("testrepo.git");
+	cl_assert(git_repository_is_bare(g_repo));
+
+	cl_git_pass(git_repository_index(&index, g_repo));
+	cl_git_pass(git_revparse_single(&head, g_repo, "HEAD^{tree}"));
+	cl_git_pass(git_index_read_tree(index, (const git_tree *)head));
+	cl_git_pass(git_index_write(index));
+	git_index_free(index);
+
+	opts.checkout_strategy = GIT_CHECKOUT_SAFE_CREATE;
+
+	opts.notify_flags = GIT_CHECKOUT_NOTIFY_ALL;
+	opts.notify_cb = checkout_count_callback;
+	opts.notify_payload = &cts;
+
+	/* fail to checkout a bare repo */
+	cl_git_fail(git_checkout_index(g_repo, NULL, &opts));
+
+	opts.target_directory = "alternative";
+	cl_assert(!git_path_isdir("alternative"));
+
+	cl_git_pass(git_checkout_index(g_repo, NULL, &opts));
+
+	cl_assert_equal_i(0, cts.n_untracked);
+	cl_assert_equal_i(0, cts.n_ignored);
+	cl_assert_equal_i(3, cts.n_updates);
+
+	check_file_contents("./alternative/README", "hey there\n");
+	check_file_contents("./alternative/branch_file.txt", "hi\nbye!\n");
+	check_file_contents("./alternative/new.txt", "my new file\n");
+
+	cl_git_pass(git_futils_rmdir_r(
+		"alternative", NULL, GIT_RMDIR_REMOVE_FILES));
+}
+
+void test_checkout_index__can_get_repo_from_index(void)
+{
+	git_index *index;
+	git_checkout_opts opts = GIT_CHECKOUT_OPTS_INIT;
+
+	cl_assert_equal_i(false, git_path_isfile("./testrepo/README"));
+	cl_assert_equal_i(false, git_path_isfile("./testrepo/branch_file.txt"));
+	cl_assert_equal_i(false, git_path_isfile("./testrepo/new.txt"));
+
+	opts.checkout_strategy = GIT_CHECKOUT_SAFE_CREATE;
+
+	cl_git_pass(git_repository_index(&index, g_repo));
+
+	cl_git_pass(git_checkout_index(NULL, index, &opts));
+
+	check_file_contents("./testrepo/README", "hey there\n");
+	check_file_contents("./testrepo/branch_file.txt", "hi\nbye!\n");
+	check_file_contents("./testrepo/new.txt", "my new file\n");
+
+	git_index_free(index);
+}
diff --git a/tests-clar/checkout/tree.c b/tests-clar/checkout/tree.c
index 5835ab0..0e65f28 100644
--- a/tests-clar/checkout/tree.c
+++ b/tests-clar/checkout/tree.c
@@ -596,6 +596,8 @@ void test_checkout_tree__fails_when_dir_in_use(void)
 	cl_git_pass(p_chdir("../.."));
 
 	cl_assert(git_path_is_empty_dir("testrepo/a"));
+
+	git_object_free(obj);
 #endif
 }
 
@@ -628,5 +630,47 @@ void test_checkout_tree__can_continue_when_dir_in_use(void)
 	cl_git_pass(p_chdir("../.."));
 
 	cl_assert(git_path_is_empty_dir("testrepo/a"));
+
+	git_object_free(obj);
 #endif
 }
+
+void test_checkout_tree__target_directory_from_bare(void)
+{
+	git_checkout_opts opts = GIT_CHECKOUT_OPTS_INIT;
+	git_oid oid;
+	checkout_counts cts;
+	memset(&cts, 0, sizeof(cts));
+
+	test_checkout_tree__cleanup(); /* cleanup default checkout */
+
+	g_repo = cl_git_sandbox_init("testrepo.git");
+	cl_assert(git_repository_is_bare(g_repo));
+
+	opts.checkout_strategy = GIT_CHECKOUT_SAFE_CREATE;
+
+	opts.notify_flags = GIT_CHECKOUT_NOTIFY_ALL;
+	opts.notify_cb = checkout_count_callback;
+	opts.notify_payload = &cts;
+
+	cl_git_pass(git_reference_name_to_id(&oid, g_repo, "HEAD"));
+	cl_git_pass(git_object_lookup(&g_object, g_repo, &oid, GIT_OBJ_ANY));
+
+	cl_git_fail(git_checkout_tree(g_repo, g_object, &opts));
+
+	opts.target_directory = "alternative";
+	cl_assert(!git_path_isdir("alternative"));
+
+	cl_git_pass(git_checkout_tree(g_repo, g_object, &opts));
+
+	cl_assert_equal_i(0, cts.n_untracked);
+	cl_assert_equal_i(0, cts.n_ignored);
+	cl_assert_equal_i(3, cts.n_updates);
+
+	check_file_contents("./alternative/README", "hey there\n");
+	check_file_contents("./alternative/branch_file.txt", "hi\nbye!\n");
+	check_file_contents("./alternative/new.txt", "my new file\n");
+
+	cl_git_pass(git_futils_rmdir_r(
+		"alternative", NULL, GIT_RMDIR_REMOVE_FILES));
+}