Understand `--' to end processing of command options.

This means one search for a string starting with a dash.
Fix also filenames starting with a dash. Close PR #3349

gnu/usr.bin/gzip/zgrep.getopt

@@ -26,7 +26,7 @@
 #
 # zgrep - search possibly compressed files for a regular expression
 #
-# $Id$
+# $Id: zgrep.getopt,v 1.4 1997/02/22 15:46:11 peter Exp $
 
 
 PATH=/bin:/usr/bin:$PATH; export PATH
@@ -67,7 +67,7 @@ files="$@"
 # no shell loop neccessary for option -q or -h 
 # and a single file or reading from stdin
 case "$header"X"$#" in 
-	-h*|-q*|X0|X1) 	$gzip $gzipopt $files | $grep $grepopt $pattern
+	-h*|-q*|X0|X1) 	$gzip $gzipopt -- $files | $grep $grepopt -- $pattern
 			exit $?;; 
 esac
 
@@ -76,13 +76,13 @@ exit=1
 for f in $files
 do
 	case "$line" in
-		-l|-L) 	if $gzip $gzipopt $f | 
-				$grep $grepopt $pattern >/dev/null
+		-l|-L) 	if $gzip $gzipopt -- $f | 
+				$grep $grepopt -- $pattern >/dev/null
 			then
 				echo $f
 			fi
 			;;
-		*) $gzip $gzipopt $f | $grep $grepopt $pattern | 
+		*) $gzip $gzipopt -- $f | $grep $grepopt -- $pattern | 
 			sed "s%^%${f}:%";;
 	esac