parse: Don't treat -mount differently from -xdev yet

The new POSIX version with -mount isn't out yet, so there's no point in
conforming to a non-existent document while breaking compatibility with
GNU find, which hasn't changed yet either.  But a warning is added for
the future incompatibility.  This patch can be reverted to re-enable the
feature.

Author: tavianator

parse.c

@@ -1543,7 +1543,14 @@ static struct expr *parse_ls(struct parser_state *state, int arg1, int arg2) {
  * Parse -mount.
  */
 static struct expr *parse_mount(struct parser_state *state, int arg1, int arg2) {
-	state->cmdline->flags |= BFTW_MOUNT;
+	if (state->warn) {
+		parse_warning(state,
+		              "In the future, %s will skip mount points entirely, unlike\n"
+		              "-xdev, due to http://austingroupbugs.net/view.php?id=1133.\n\n",
+		              state->argv[0]);
+	}
+
+	state->cmdline->flags |= BFTW_XDEV;
 	state->mount_arg = state->argv[0];
 	return parse_nullary_option(state);
 }

tests/test_L_mount.out

@@ -1,2 +1,5 @@
 scratch
 scratch/foo
+scratch/mnt
+scratch/foo/bar
+scratch/foo/qux

tests/test_mount.out

@@ -1,3 +1,4 @@
 scratch
 scratch/foo
+scratch/mnt
 scratch/foo/bar