newt: add 'kf' command to grep $home/lib/newsgroups for group names

rc/bin/newt

@@ -75,7 +75,7 @@ fn k{
 	kmnt=`{echo $mnt | sed 's/\//\\\//g'}
 	f $mnt/$* |
 		grep -v -e '\/([0-9]+|article|body|header|post|xover)$' |
-		sed 's/^'$"kmnt'\// g	/g' |
+		sed 's/^'$"kmnt'\//  g	/g' |
 		sort
 }
 fn nshift{ shift; echo $* }
@@ -88,6 +88,7 @@ g ...		go to specified group
 h		print message headlines
 help		print this help message
 k ...		list sub-groups under specified group
+kf ...		grep $home/lib/newsgroups for regexp
 l		jump to last message
 n		next
 p		print message with minimal headers
@@ -194,6 +195,9 @@ while(){
 		k $group
 	case k' '*
 		k `{nshift $cmd | sed 's/\./\//g'}
+	case kf' '*
+		grep -e `{nshift $cmd} $home/lib/newsgroups |
+			sed 's/^/  g	/g'
 	case l
 		post=$posts($#posts)
 		printp $post

sys/man/1/newt

@@ -85,6 +85,13 @@ available sub-group. When provided with an argument,
 it instead walks the directories under the group specified
 by the argument.
 .TP
+.BI kf " regexp
+Greps
+.B $home/lib/newsgroups
+for
+.I regexp
+and prints commands suitable for changing to each match.
+.TP
 .B l
 Jump to the last message in the group.
 .TP
@@ -118,6 +125,9 @@ with the whole message as standard input.
 .TP
 \fB"\fP
 Print the current message in quoted form, suitable for reply.
+.SH FILES
+.B $home/lib/newsgroups
+list of newsgroups, one per line
 .SH SOURCE
 .B /rc/bin/newt
 .SH "SEE ALSO"
@@ -126,7 +136,9 @@ Print the current message in quoted form, suitable for reply.
 The list of available newsgroups offered by a given server
 may be quite large. This complicates walking the list over 
 a slow Internet connection, and renders searching in real-time
-all but infeasible.
+all but infeasible. Grepping a pre-generated
+.B newsgroups
+file is a compromise.
 .SH HISTORY
 .I Newt
 first appeared in 9front (April, 2014).