dir-iterator: drop unused `DIR_ITERATOR_FOLLOW_SYMLINKS`

The `FOLLOW_SYMLINKS` flag was added to the dir-iterator API in
fa1da7d2ee (dir-iterator: add flags parameter to dir_iterator_begin,
2019-07-10) in order to follow symbolic links while traversing through a
directory.

`FOLLOW_SYMLINKS` gained its first caller in ff7ccc8c9a (clone: use
dir-iterator to avoid explicit dir traversal, 2019-07-10), but it was
subsequently removed in 6f054f9fb3 (builtin/clone.c: disallow `--local`
clones with symlinks, 2022-07-28).

Since then, we've held on to the code for `DIR_ITERATOR_FOLLOW_SYMLINKS`
in the name of making minimally invasive changes during a security
embargo.

In fact, we even changed the dir-iterator API in bffc762f87
(dir-iterator: prevent top-level symlinks without FOLLOW_SYMLINKS,
2023-01-24) without having any non-test callers of that flag.

Now that we're past those security embargo(s), let's finalize our
cleanup of the `DIR_ITERATOR_FOLLOW_SYMLINKS` code and remove its
implementation since there are no remaining callers.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

dir-iterator.c

@@ -112,9 +112,6 @@ static int prepare_next_entry_data(struct dir_iterator_int *iter,
 	iter->base.basename = iter->base.path.buf +
 			      iter->levels[iter->levels_nr - 1].prefix_len;
 
-	if (iter->flags & DIR_ITERATOR_FOLLOW_SYMLINKS)
-		err = stat(iter->base.path.buf, &iter->base.st);
-	else
 	err = lstat(iter->base.path.buf, &iter->base.st);
 
 	saved_errno = errno;
@@ -213,12 +210,9 @@ struct dir_iterator *dir_iterator_begin(const char *path, unsigned int flags)
 	iter->flags = flags;
 
 	/*
-	 * Note: stat/lstat already checks for NULL or empty strings and
+	 * Note: lstat already checks for NULL or empty strings and
 	 * nonexistent paths.
 	 */
-	if (iter->flags & DIR_ITERATOR_FOLLOW_SYMLINKS)
-		err = stat(iter->base.path.buf, &iter->base.st);
-	else
 	err = lstat(iter->base.path.buf, &iter->base.st);
 
 	if (err < 0) {

dir-iterator.h

@@ -54,24 +54,8 @@
  *   and ITER_ERROR is returned immediately. In both cases, a meaningful
  *   warning is emitted. Note: ENOENT errors are always ignored so that
  *   the API users may remove files during iteration.
- *
- * - DIR_ITERATOR_FOLLOW_SYMLINKS: make dir-iterator follow symlinks.
- *   i.e., linked directories' contents will be iterated over and
- *   iter->base.st will contain information on the referred files,
- *   not the symlinks themselves, which is the default behavior. Broken
- *   symlinks are ignored.
- *
- *   Note: setting DIR_ITERATOR_FOLLOW_SYMLINKS affects resolving the
- *   starting path as well (e.g., attempting to iterate starting at a
- *   symbolic link pointing to a directory without FOLLOW_SYMLINKS will
- *   result in an error).
- *
- * Warning: circular symlinks are also followed when
- * DIR_ITERATOR_FOLLOW_SYMLINKS is set. The iteration may end up with
- * an ELOOP if they happen and DIR_ITERATOR_PEDANTIC is set.
  */
 #define DIR_ITERATOR_PEDANTIC (1 << 0)
-#define DIR_ITERATOR_FOLLOW_SYMLINKS (1 << 1)
 
 struct dir_iterator {
 	/* The current path: */
@@ -88,9 +72,7 @@ struct dir_iterator {
 	const char *basename;
 
 	/*
-	 * The result of calling lstat() on path; or stat(), if the
-	 * DIR_ITERATOR_FOLLOW_SYMLINKS flag was set at
-	 * dir_iterator's initialization.
+	 * The result of calling lstat() on path.
 	 */
 	struct stat st;
 };

t/helper/test-dir-iterator.c

@@ -15,7 +15,7 @@ static const char *error_name(int error_number)
 
 /*
  * usage:
- * tool-test dir-iterator [--follow-symlinks] [--pedantic] directory_path
+ * tool-test dir-iterator [--pedantic] directory_path
  */
 int cmd__dir_iterator(int argc, const char **argv)
 {
@@ -24,9 +24,7 @@ int cmd__dir_iterator(int argc, const char **argv)
 	int iter_status;
 
 	for (++argv, --argc; *argv && starts_with(*argv, "--"); ++argv, --argc) {
-		if (strcmp(*argv, "--follow-symlinks") == 0)
-			flags |= DIR_ITERATOR_FOLLOW_SYMLINKS;
-		else if (strcmp(*argv, "--pedantic") == 0)
+		if (strcmp(*argv, "--pedantic") == 0)
 			flags |= DIR_ITERATOR_PEDANTIC;
 		else
 			die("invalid option '%s'", *argv);

t/t0066-dir-iterator.sh

@@ -131,44 +131,10 @@ test_expect_success SYMLINKS 'dir-iterator should not follow symlinks by default
 	test_cmp expected-no-follow-sorted-output actual-no-follow-sorted-output
 '
 
-test_expect_success SYMLINKS 'dir-iterator should follow symlinks w/ follow flag' '
-	cat >expected-follow-sorted-output <<-EOF &&
-	[d] (a) [a] ./dir4/a
-	[d] (a/f) [f] ./dir4/a/f
-	[d] (a/f/c) [c] ./dir4/a/f/c
-	[d] (b) [b] ./dir4/b
-	[d] (b/c) [c] ./dir4/b/c
-	[f] (a/d) [d] ./dir4/a/d
-	[f] (a/e) [e] ./dir4/a/e
-	EOF
-
-	test-tool dir-iterator --follow-symlinks ./dir4 >out &&
-	sort out >actual-follow-sorted-output &&
-
-	test_cmp expected-follow-sorted-output actual-follow-sorted-output
-'
-
 test_expect_success SYMLINKS 'dir-iterator does not resolve top-level symlinks' '
 	test_must_fail test-tool dir-iterator ./dir6 >out &&
 
 	grep "ENOTDIR" out
 '
 
-test_expect_success SYMLINKS 'dir-iterator resolves top-level symlinks w/ follow flag' '
-	cat >expected-follow-sorted-output <<-EOF &&
-	[d] (a) [a] ./dir6/a
-	[d] (a/f) [f] ./dir6/a/f
-	[d] (a/f/c) [c] ./dir6/a/f/c
-	[d] (b) [b] ./dir6/b
-	[d] (b/c) [c] ./dir6/b/c
-	[f] (a/d) [d] ./dir6/a/d
-	[f] (a/e) [e] ./dir6/a/e
-	EOF
-
-	test-tool dir-iterator --follow-symlinks ./dir6 >out &&
-	sort out >actual-follow-sorted-output &&
-
-	test_cmp expected-follow-sorted-output actual-follow-sorted-output
-'
-
 test_done