Merge branch 'jk/shell-no-repository-that-begins-with-dash' into maint-2.4

* jk/shell-no-repository-that-begins-with-dash:
  shell: disallow repo names beginning with dash

shell.c

@@ -13,7 +13,7 @@ static int do_generic_cmd(const char *me, char *arg)
 	const char *my_argv[4];
 
 	setup_path();
-	if (!arg || !(arg = sq_dequote(arg)))
+	if (!arg || !(arg = sq_dequote(arg)) || *arg == '-')
 		die("bad argument");
 	if (!starts_with(me, "git-"))
 		die("bad command");