add silent flag from Ubuntu to witch

sh/witch

@@ -4,10 +4,11 @@
 ### this is a personal rewrite of `which` from Debian.
 ### the original version didn't run on certain shells,
 ### and inherited inconsistent behaviors from getopts.
+### the silent (`-s`) flag from Ubuntu has been added.
 
 set -ef
 
-all=0
+all=0 silent=0
 for flag; do
 	case "$flag" in
 	(--) shift; break;;
@@ -16,6 +17,7 @@ for flag; do
 		while flag="${flag#?}"; [ -n "$flag" ]; do
 			case "$flag" in
 			(a*) all=1;;
+			(s*) silent=1;;
 			(*)
 				printf >&2 'Illegal option: -%.1s\n' "$flag"
 				printf 'Usage: %s\n' "$0 [-a] args"
@@ -28,13 +30,19 @@ done
 
 [ "$#" = 0 ] && res=1 || res=0
 
+if [ "$silent" = 0 ]; then
+	puts() { printf %s\\n "$@"; }
+else
+	puts() { :; }
+fi
+
 IFS=:
 for prog; do
 	err=1
 	case "$prog" in
 	(*/*)
 		if [ -f "$prog" ] && [ -x "$prog" ]; then
-			printf %s\\n "$prog"
+			puts "$prog"
 			err=0
 		fi;;
 	(*)
@@ -42,7 +50,7 @@ for prog; do
 		for sub; do
 			[ -n "$sub" ] || sub=.
 			if [ -f "$sub/$prog" ] && [ -x "$sub/$prog" ]; then
-				printf %s\\n "$sub/$prog"
+				puts "$sub/$prog"
 				err=0
 				[ "$all" = 1 ] || break
 			fi