Avoid a server-side problem with -e is at the start of the short options.

(Bug #6020)

support/rrsync

@@ -143,7 +143,8 @@ while ($command =~ /((?:[^\s\\]+|\\.[^\s\\]*)+)/g) {
     if ($_ eq '.') {
       $in_options = 0;
     } else {
-      next if /^-$short_no_arg+(e\d*\.\w*)?$/o || /^-$short_with_num\d+$/o;
+      die "$0: invalid option: '-'\n" if $_ eq '-';
+      next if /^-$short_no_arg*(e\d*\.\w*)?$/o || /^-$short_with_num\d+$/o;
 
       my($opt,$arg) = /^--([^=]+)(?:=(.*))?$/;
       my $disabled;