Allow more than one rule per mailing list

src/freedombone-addlist

 shift
 done
 
-if ! [[ $MYUSERNAME ]]; then
+if [ ! $MYUSERNAME ]; then
     show_help
 fi
+
 if [[ ! $MAILINGLIST && ! $SUBJECTTAG ]]; then
     show_help
 fi
 PM=/home/$MYUSERNAME/.procmailrc
 LISTDIR=/home/$MYUSERNAME/Maildir/$MAILINGLIST
 
-# Exit if the list was already added
 if grep -q "=$MAILINGLIST" $MUTTRC; then
-    exit 54678
+    echo $"Mailing list $MAILINGLIST was already added"
 fi
 
 if [ ! -d "$LISTDIR" ]; then
 
 MUTT_MAILBOXES=$(grep "mailboxes =" $MUTTRC)
 if [[ $MUTT_MAILBOXES != *$MAILINGLIST* ]]; then
-    sed -i "s|$MUTT_MAILBOXES|$MUTT_MAILBOXES =$MAILINGLIST|g" $MUTTRC
-    chown $MYUSERNAME:$MYUSERNAME $MUTTRC
+    if ! grep -q "=$MAILINGLIST" $MUTTRC; then
+        sed -i "s|$MUTT_MAILBOXES|$MUTT_MAILBOXES =$MAILINGLIST|g" $MUTTRC
+        chown $MYUSERNAME:$MYUSERNAME $MUTTRC
+    fi
 fi
 
 if [ $LIST_ADDRESS ]; then