allow empty dirs to exist when doing checkout

src/checkout.c

@@ -467,6 +467,7 @@ static int checkout_action(
 	int cmp = -1, act;
 	int (*strcomp)(const char *, const char *) = data->diff->strcomp;
 	int (*pfxcomp)(const char *str, const char *pfx) = data->diff->pfxcomp;
+	int error;
 
 	/* move workdir iterator to follow along with deltas */
 
@@ -490,8 +491,11 @@ static int checkout_action(
 			if (cmp == 0) {
 				if (wd->mode == GIT_FILEMODE_TREE) {
 					/* case 2 - entry prefixed by workdir tree */
-					if (git_iterator_advance_into(&wd, workdir) < 0)
-						goto fail;
+					if ((error = git_iterator_advance_into(&wd, workdir)) < 0) {
+						if (error != GIT_ENOTFOUND ||
+							git_iterator_advance(&wd, workdir) < 0)
+							goto fail;
+					}
 
 					*wditem_ptr = wd;
 					continue;

tests-clar/checkout/tree.c

@@ -501,3 +501,28 @@ void test_checkout_tree__issue_1397(void)
 
 	git_object_free(tree);
 }
+
+void test_checkout_tree__can_write_to_empty_dirs(void)
+{
+	git_checkout_opts opts = GIT_CHECKOUT_OPTS_INIT;
+	git_oid oid;
+	git_object *obj = NULL;
+
+	assert_on_branch(g_repo, "master");
+
+	cl_git_pass(p_mkdir("testrepo/a", 0777));
+
+	/* do first checkout with FORCE because we don't know if testrepo
+	 * base data is clean for a checkout or not
+	 */
+	opts.checkout_strategy = GIT_CHECKOUT_FORCE;
+
+	cl_git_pass(git_reference_name_to_id(&oid, g_repo, "refs/heads/dir"));
+	cl_git_pass(git_object_lookup(&obj, g_repo, &oid, GIT_OBJ_ANY));
+
+	cl_git_pass(git_checkout_tree(g_repo, obj, &opts));
+
+	cl_assert(git_path_isfile("testrepo/a/b.txt"));
+
+	git_object_free(obj);
+}