Improve iterator ignoring .git file

The workdir iterator has always tried to ignore .git files, but
it turns out there were some bugs.  This makes it more robust at
ignoring .git files.

This also makes iterators always check ".git" case insensitively
regardless of the properties of the system.  This will make libgit2
skip ".GIT" and the like.  This is different from core git, but on
systems with case insensitive but case preserving file systems,
allowing ".GIT" to be added is problematic.

src/iterator.c

@@ -10,6 +10,7 @@
 #include "ignore.h"
 #include "buffer.h"
 #include "git2/submodule.h"
+#include <ctype.h>
 
 #define ITERATOR_BASE_INIT(P,NAME_LC,NAME_UC) do { \
 	(P) = git__calloc(1, sizeof(NAME_LC ## _iterator)); \
@@ -465,6 +466,23 @@ static int git_path_with_stat_cmp_icase(const void *a, const void *b)
 	return strcasecmp(path_with_stat_a->path, path_with_stat_b->path);
 }
 
+GIT_INLINE(bool) path_is_dotgit(const git_path_with_stat *ps)
+{
+	if (!ps)
+		return false;
+	else {
+		const char *path = ps->path;
+		size_t len  = ps->path_len;
+
+		return len >= 4 &&
+			tolower(path[len - 1]) == 't' &&
+			tolower(path[len - 2]) == 'i' &&
+			tolower(path[len - 3]) == 'g' &&
+			path[len - 4] == '.' &&
+			(len == 4 || path[len - 5] == '/');
+	}
+}
+
 static workdir_iterator_frame *workdir_iterator__alloc_frame(workdir_iterator *wi)
 {
 	workdir_iterator_frame *wf = git__calloc(1, sizeof(workdir_iterator_frame));
@@ -531,6 +549,9 @@ static int workdir_iterator__expand_dir(workdir_iterator *wi)
 			CASESELECT(wi->base.ignore_case, workdir_iterator__entry_cmp_icase, workdir_iterator__entry_cmp_case),
 			wf->start);
 
+	if (path_is_dotgit(git_vector_get(&wf->entries, wf->index)))
+		wf->index++;
+
 	wf->next  = wi->stack;
 	wi->stack = wf;
 
@@ -574,8 +595,7 @@ static int workdir_iterator__advance(
 		next = git_vector_get(&wf->entries, ++wf->index);
 		if (next != NULL) {
 			/* match git's behavior of ignoring anything named ".git" */
-			if (STRCMP_CASESELECT(wi->base.ignore_case, next->path, DOT_GIT "/") == 0 ||
-				STRCMP_CASESELECT(wi->base.ignore_case, next->path, DOT_GIT) == 0)
+			if (path_is_dotgit(next))
 				continue;
 			/* else found a good entry */
 			break;
@@ -658,8 +678,7 @@ static int workdir_iterator__update_entry(workdir_iterator *wi)
 	wi->entry.path = ps->path;
 
 	/* skip over .git entries */
-	if (STRCMP_CASESELECT(wi->base.ignore_case, ps->path, DOT_GIT "/") == 0 ||
-		STRCMP_CASESELECT(wi->base.ignore_case, ps->path, DOT_GIT) == 0)
+	if (path_is_dotgit(ps))
 		return workdir_iterator__advance((git_iterator *)wi, NULL);
 
 	wi->is_ignored = -1;

tests-clar/diff/iterator.c

@@ -668,3 +668,59 @@ void test_diff_iterator__workdir_1_ranged_empty_2(void)
 		"status", NULL, "aaaa_empty_before",
 		0, 0, NULL, NULL);
 }
+
+void test_diff_iterator__workdir_builtin_ignores(void)
+{
+	git_repository *repo = cl_git_sandbox_init("attr");
+	git_iterator *i;
+	const git_index_entry *entry;
+	int idx;
+	static struct {
+		const char *path;
+		bool ignored;
+	} expected[] = {
+		{ "dir/", true },
+		{ "file", false },
+		{ "ign", true },
+		{ "macro_bad", false },
+		{ "macro_test", false },
+		{ "root_test1", false },
+		{ "root_test2", false },
+		{ "root_test3", false },
+		{ "root_test4.txt", false },
+		{ "sub/", false },
+		{ "sub/.gitattributes", false },
+		{ "sub/abc", false },
+		{ "sub/dir/", true },
+		{ "sub/file", false },
+		{ "sub/ign/", true },
+		{ "sub/sub/", false },
+		{ "sub/sub/.gitattributes", false },
+		{ "sub/sub/dir", false }, /* file is not actually a dir */
+		{ "sub/sub/file", false },
+		{ NULL, false }
+	};
+
+	cl_git_pass(p_mkdir("attr/sub/sub/.git", 0777));
+	cl_git_mkfile("attr/sub/.git", "whatever");
+
+	cl_git_pass(
+		git_iterator_for_workdir_range(&i, repo, "dir", "sub/sub/file"));
+	cl_git_pass(git_iterator_current(i, &entry));
+
+	for (idx = 0; entry != NULL; ++idx) {
+		int ignored = git_iterator_current_is_ignored(i);
+
+		cl_assert_equal_s(expected[idx].path, entry->path);
+		cl_assert_(ignored == expected[idx].ignored, expected[idx].path);
+
+		if (!ignored && S_ISDIR(entry->mode))
+			cl_git_pass(git_iterator_advance_into_directory(i, &entry));
+		else
+			cl_git_pass(git_iterator_advance(i, &entry));
+	}
+
+	cl_assert(expected[idx].path == NULL);
+
+	git_iterator_free(i);
+}