Fix {update,checkout}-index usage strings

The `<file>' argument is optional in both cases (the man pages are
already correct).

Signed-off-by: Štěpán Němec <stepnem@gmail.com>
Acked-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/checkout-index.c

@@ -155,7 +155,7 @@ static void checkout_all(const char *prefix, int prefix_length)
 }
 
 static const char * const builtin_checkout_index_usage[] = {
-	"git checkout-index [options] [--] <file>...",
+	"git checkout-index [options] [--] [<file>...]",
 	NULL
 };
 

builtin/update-index.c

@@ -398,7 +398,7 @@ static void read_index_info(int line_termination)
 }
 
 static const char update_index_usage[] =
-"git update-index [-q] [--add] [--replace] [--remove] [--unmerged] [--refresh] [--really-refresh] [--cacheinfo] [--chmod=(+|-)x] [--assume-unchanged] [--skip-worktree|--no-skip-worktree] [--info-only] [--force-remove] [--stdin] [--index-info] [--unresolve] [--again | -g] [--ignore-missing] [-z] [--verbose] [--] <file>...";
+"git update-index [-q] [--add] [--replace] [--remove] [--unmerged] [--refresh] [--really-refresh] [--cacheinfo] [--chmod=(+|-)x] [--assume-unchanged] [--skip-worktree|--no-skip-worktree] [--info-only] [--force-remove] [--stdin] [--index-info] [--unresolve] [--again | -g] [--ignore-missing] [-z] [--verbose] [--] [<file>...]";
 
 static unsigned char head_sha1[20];
 static unsigned char merge_head_sha1[20];