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/check-ignore.c

@@ -4,6 +4,7 @@
 #include "quote.h"
 #include "pathspec.h"
 #include "parse-options.h"
+#include "submodule.h"
 
 static int quiet, verbose, stdin_paths, show_non_matching, no_index;
 static const char * const check_ignore_usage[] = {
@@ -87,10 +88,11 @@ static int check_ignore(struct dir_struct *dir,
 	parse_pathspec(&pathspec,
 		       PATHSPEC_ALL_MAGIC & ~PATHSPEC_FROMTOP,
 		       PATHSPEC_SYMLINK_LEADING_PATH |
-		       PATHSPEC_STRIP_SUBMODULE_SLASH_EXPENSIVE |
 		       PATHSPEC_KEEP_ORDER,
 		       prefix, argv);
 
+	die_path_inside_submodule(&the_index, &pathspec);
+
 	/*
 	 * look for pathspecs matching entries in the index, since these
 	 * should not be ignored, in order to be consistent with