pathspec: remove PATHSPEC_STRIP_SUBMODULE_SLASH_EXPENSIVE flag

Since (ae8d08242 pathspec: pass directory indicator to
match_pathspec_item()) the path matching logic has been able to cope
with submodules without needing to strip off a trailing slash if a path
refers to a submodule.

Since the stripping the trailing slash is no longer necessary, remove
the PATHSPEC_STRIP_SUBMODULE_SLASH_EXPENSIVE flag.  In addition, factor
out the logic which dies if a path decends into a submodule so that it
can still be used as a check after a pathspec struct has been
initialized.

Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/add.c

@@ -388,10 +388,11 @@ int cmd_add(int argc, const char **argv, const char *prefix)
 	 */
 	parse_pathspec(&pathspec, 0,
 		       PATHSPEC_PREFER_FULL |
-		       PATHSPEC_SYMLINK_LEADING_PATH |
-		       PATHSPEC_STRIP_SUBMODULE_SLASH_EXPENSIVE,
+		       PATHSPEC_SYMLINK_LEADING_PATH,
 		       prefix, argv);
 
+	die_path_inside_submodule(&the_index, &pathspec);
+
 	if (add_new_files) {
 		int baselen;