Ranged iterators and rewritten git_status_file

The goal of this work is to rewrite git_status_file to use the
same underlying code as git_status_foreach.

This is done in 3 phases:

1. Extend iterators to allow ranged iteration with start and
   end prefixes for the range of file names to be covered.
2. Improve diff so that when there is a pathspec and there is
   a common non-wildcard prefix of the pathspec, it will use
   ranged iterators to minimize excess iteration.
3. Rewrite git_status_file to call git_status_foreach_ext
   with a pathspec that covers just the one file being checked.

Since ranged iterators underlie the status & diff implementation,
this is actually fairly efficient.  The workdir iterator does
end up loading the contents of all the directories down to the
single file, which should ideally be avoided, but it is pretty
good.

1 files changed, 208 insertions, 14 deletions

diff --git a/tests-clar/diff/iterator.c b/tests-clar/diff/iterator.c
index 0ec2326eb..be29bea66 100644
--- a/tests-clar/diff/iterator.c
+++ b/tests-clar/diff/iterator.c
@@ -22,6 +22,8 @@ void test_diff_iterator__cleanup(void)
 static void tree_iterator_test(
 	const char *sandbox,
 	const char *treeish,
+	const char *start,
+	const char *end,
 	int expected_count,
 	const char **expected_values)
 {
@@ -32,7 +34,7 @@ static void tree_iterator_test(
 	git_repository *repo = cl_git_sandbox_init(sandbox);
 
 	cl_assert(t = resolve_commit_oid_to_tree(repo, treeish));
-	cl_git_pass(git_iterator_for_tree(repo, t, &i));
+	cl_git_pass(git_iterator_for_tree_range(&i, repo, t, start, end));
 	cl_git_pass(git_iterator_current(i, &entry));
 
 	while (entry != NULL) {
@@ -74,7 +76,7 @@ const char *expected_tree_0[] = {
 
 void test_diff_iterator__tree_0(void)
 {
-	tree_iterator_test("attr", "605812a", 16, expected_tree_0);
+	tree_iterator_test("attr", "605812a", NULL, NULL, 16, expected_tree_0);
 }
 
 /* results of: git ls-tree -r --name-only 6bab5c79 */
@@ -97,7 +99,7 @@ const char *expected_tree_1[] = {
 
 void test_diff_iterator__tree_1(void)
 {
-	tree_iterator_test("attr", "6bab5c79cd5", 13, expected_tree_1);
+	tree_iterator_test("attr", "6bab5c79cd5", NULL, NULL, 13, expected_tree_1);
 }
 
 /* results of: git ls-tree -r --name-only 26a125ee1 */
@@ -119,7 +121,7 @@ const char *expected_tree_2[] = {
 
 void test_diff_iterator__tree_2(void)
 {
-	tree_iterator_test("status", "26a125ee1", 12, expected_tree_2);
+	tree_iterator_test("status", "26a125ee1", NULL, NULL, 12, expected_tree_2);
 }
 
 /* $ git ls-tree -r --name-only 0017bd4ab1e */
@@ -136,7 +138,7 @@ const char *expected_tree_3[] = {
 
 void test_diff_iterator__tree_3(void)
 {
-	tree_iterator_test("status", "0017bd4ab1e", 8, expected_tree_3);
+	tree_iterator_test("status", "0017bd4ab1e", NULL, NULL, 8, expected_tree_3);
 }
 
 /* $ git ls-tree -r --name-only 24fa9a9fc4e202313e24b648087495441dab432b */
@@ -170,14 +172,77 @@ const char *expected_tree_4[] = {
 void test_diff_iterator__tree_4(void)
 {
 	tree_iterator_test(
-		"attr", "24fa9a9fc4e202313e24b648087495441dab432b",
+		"attr", "24fa9a9fc4e202313e24b648087495441dab432b", NULL, NULL,
 		23, expected_tree_4);
 }
 
+void test_diff_iterator__tree_4_ranged(void)
+{
+	tree_iterator_test(
+		"attr", "24fa9a9fc4e202313e24b648087495441dab432b",
+		"sub", "sub",
+		11, &expected_tree_4[12]);
+}
+
+const char *expected_tree_ranged_0[] = {
+	"gitattributes",
+	"macro_bad",
+	"macro_test",
+	"root_test1",
+	"root_test2",
+	"root_test3",
+	"root_test4.txt",
+	NULL
+};
+
+void test_diff_iterator__tree_ranged_0(void)
+{
+	tree_iterator_test(
+		"attr", "24fa9a9fc4e202313e24b648087495441dab432b",
+		"git", "root",
+		7, expected_tree_ranged_0);
+}
+
+const char *expected_tree_ranged_1[] = {
+	"sub/subdir_test2.txt",
+	NULL
+};
+
+void test_diff_iterator__tree_ranged_1(void)
+{
+	tree_iterator_test(
+		"attr", "24fa9a9fc4e202313e24b648087495441dab432b",
+		"sub/subdir_test2.txt", "sub/subdir_test2.txt",
+		1, expected_tree_ranged_1);
+}
+
+void test_diff_iterator__tree_range_empty_0(void)
+{
+	tree_iterator_test(
+		"attr", "24fa9a9fc4e202313e24b648087495441dab432b",
+		"empty", "empty", 0, NULL);
+}
+
+void test_diff_iterator__tree_range_empty_1(void)
+{
+	tree_iterator_test(
+		"attr", "24fa9a9fc4e202313e24b648087495441dab432b",
+		"z_empty_after", NULL, 0, NULL);
+}
+
+void test_diff_iterator__tree_range_empty_2(void)
+{
+	tree_iterator_test(
+		"attr", "24fa9a9fc4e202313e24b648087495441dab432b",
+		NULL, ".aaa_empty_before", 0, NULL);
+}
+
 /* -- INDEX ITERATOR TESTS -- */
 
 static void index_iterator_test(
 	const char *sandbox,
+	const char *start,
+	const char *end,
 	int expected_count,
 	const char **expected_names,
 	const char **expected_oids)
@@ -187,7 +252,7 @@ static void index_iterator_test(
 	int count = 0;
 	git_repository *repo = cl_git_sandbox_init(sandbox);
 
-	cl_git_pass(git_iterator_for_index(repo, &i));
+	cl_git_pass(git_iterator_for_index_range(&i, repo, start, end));
 	cl_git_pass(git_iterator_current(i, &entry));
 
 	while (entry != NULL) {
@@ -197,7 +262,7 @@ static void index_iterator_test(
 		if (expected_oids != NULL) {
 			git_oid oid;
 			cl_git_pass(git_oid_fromstr(&oid, expected_oids[count]));
-			cl_assert(git_oid_cmp(&oid, &entry->oid) == 0);
+			cl_assert_equal_i(git_oid_cmp(&oid, &entry->oid), 0);
 		}
 
 		count++;
@@ -206,7 +271,7 @@ static void index_iterator_test(
 
 	git_iterator_free(i);
 
-	cl_assert(count == expected_count);
+	cl_assert_equal_i(expected_count, count);
 }
 
 static const char *expected_index_0[] = {
@@ -263,7 +328,46 @@ static const char *expected_index_oids_0[] = {
 
 void test_diff_iterator__index_0(void)
 {
-	index_iterator_test("attr", 23, expected_index_0, expected_index_oids_0);
+	index_iterator_test(
+		"attr", NULL, NULL, 23, expected_index_0, expected_index_oids_0);
+}
+
+static const char *expected_index_range[] = {
+	"root_test1",
+	"root_test2",
+	"root_test3",
+	"root_test4.txt",
+};
+
+static const char *expected_index_oids_range[] = {
+	"45141a79a77842c59a63229403220a4e4be74e3d",
+	"4d713dc48e6b1bd75b0d61ad078ba9ca3a56745d",
+	"108bb4e7fd7b16490dc33ff7d972151e73d7166e",
+	"fe773770c5a6cc7185580c9204b1ff18a33ff3fc",
+};
+
+void test_diff_iterator__index_range(void)
+{
+	index_iterator_test(
+		"attr", "root", "root", 4, expected_index_range, expected_index_oids_range);
+}
+
+void test_diff_iterator__index_range_empty_0(void)
+{
+	index_iterator_test(
+		"attr", "empty", "empty", 0, NULL, NULL);
+}
+
+void test_diff_iterator__index_range_empty_1(void)
+{
+	index_iterator_test(
+		"attr", "z_empty_after", NULL, 0, NULL, NULL);
+}
+
+void test_diff_iterator__index_range_empty_2(void)
+{
+	index_iterator_test(
+		"attr", NULL, ".aaa_empty_before", 0, NULL, NULL);
 }
 
 static const char *expected_index_1[] = {
@@ -300,7 +404,8 @@ static const char* expected_index_oids_1[] = {
 
 void test_diff_iterator__index_1(void)
 {
-	index_iterator_test("status", 13, expected_index_1, expected_index_oids_1);
+	index_iterator_test(
+		"status", NULL, NULL, 13, expected_index_1, expected_index_oids_1);
 }
 
 
@@ -308,6 +413,8 @@ void test_diff_iterator__index_1(void)
 
 static void workdir_iterator_test(
 	const char *sandbox,
+	const char *start,
+	const char *end,
 	int expected_count,
 	int expected_ignores,
 	const char **expected_names,
@@ -318,7 +425,7 @@ static void workdir_iterator_test(
 	int count = 0, count_all = 0;
 	git_repository *repo = cl_git_sandbox_init(sandbox);
 
-	cl_git_pass(git_iterator_for_workdir(repo, &i));
+	cl_git_pass(git_iterator_for_workdir_range(&i, repo, start, end));
 	cl_git_pass(git_iterator_current(i, &entry));
 
 	while (entry != NULL) {
@@ -350,7 +457,7 @@ static void workdir_iterator_test(
 
 void test_diff_iterator__workdir_0(void)
 {
-	workdir_iterator_test("attr", 25, 2, NULL, "ign");
+	workdir_iterator_test("attr", NULL, NULL, 25, 2, NULL, "ign");
 }
 
 static const char *status_paths[] = {
@@ -372,5 +479,92 @@ static const char *status_paths[] = {
 
 void test_diff_iterator__workdir_1(void)
 {
-	workdir_iterator_test("status", 12, 1, status_paths, "ignored_file");
+	workdir_iterator_test(
+		"status", NULL, NULL, 12, 1, status_paths, "ignored_file");
+}
+
+static const char *status_paths_range_0[] = {
+	"staged_changes",
+	"staged_changes_modified_file",
+	"staged_delete_modified_file",
+	"staged_new_file",
+	"staged_new_file_modified_file",
+	NULL
+};
+
+void test_diff_iterator__workdir_1_ranged_0(void)
+{
+	workdir_iterator_test(
+		"status", "staged", "staged", 5, 0, status_paths_range_0, NULL);
+}
+
+static const char *status_paths_range_1[] = {
+	"modified_file", NULL
+};
+
+void test_diff_iterator__workdir_1_ranged_1(void)
+{
+	workdir_iterator_test(
+		"status", "modified_file", "modified_file",
+		1, 0, status_paths_range_1, NULL);
+}
+
+static const char *status_paths_range_3[] = {
+	"subdir.txt",
+	"subdir/current_file",
+	"subdir/modified_file",
+	NULL
+};
+
+void test_diff_iterator__workdir_1_ranged_3(void)
+{
+	workdir_iterator_test(
+		"status", "subdir", "subdir/modified_file",
+		3, 0, status_paths_range_3, NULL);
+}
+
+static const char *status_paths_range_4[] = {
+	"subdir/current_file",
+	"subdir/modified_file",
+	"subdir/new_file",
+	NULL
+};
+
+void test_diff_iterator__workdir_1_ranged_4(void)
+{
+	workdir_iterator_test(
+		"status", "subdir/", NULL, 3, 0, status_paths_range_4, NULL);
+}
+
+static const char *status_paths_range_5[] = {
+	"subdir/modified_file",
+	NULL
+};
+
+void test_diff_iterator__workdir_1_ranged_5(void)
+{
+	workdir_iterator_test(
+		"status", "subdir/modified_file", "subdir/modified_file",
+		1, 0, status_paths_range_5, NULL);
+}
+
+void test_diff_iterator__workdir_1_ranged_empty_0(void)
+{
+	workdir_iterator_test(
+		"status", "z_does_not_exist", NULL,
+		0, 0, NULL, NULL);
+}
+
+void test_diff_iterator__workdir_1_ranged_empty_1(void)
+{
+	workdir_iterator_test(
+		"status", "empty", "empty",
+		0, 0, NULL, NULL);
+}
+
+void test_diff_iterator__workdir_1_ranged_empty_2(void)
+{
+	workdir_iterator_test(
+		"status", NULL, "aaaa_empty_before",
+		0, 0, NULL, NULL);
 }