Finished implementing clear command.

cli/interface.txt

@@ -54,7 +54,8 @@ play playlist   <id | name>
 
 clear
     queue
-    playlist
+    playlist    < id | name >
+    selected playlist
     selection
 
 * Transport operations

cli/src/main/groovy/com/jdbernard/wdiwtlt/cli/CommandLineInterface.groovy

@@ -386,10 +386,28 @@ Configuration:
     private def processClear(LinkedList line) {
         def option = line.poll()
         switch(option) {
-            case 'queue': library.removeAllFromPlaylist(playQueue.id)
+            case 'queue': return library.removeAllFromPlaylist(playQueue.id)
+            case 'selected playlist':
+                if (!selection.playlist) {
+                    printLongMessage("No playlist currently selected.")
+                    return null }
+                return library.removeAllFromPlaylist(selected.playlist.id)
+            case 'playlist':
+                def criteria = line.poll()
+                if (!criteria) {
+                    printLongMessage("Missing playlist id or name. Use " +
+                        "${promptStyle}help clear${normalStyle} to see a " +
+                        "list of valid options.")
+                    return null }
+                def playlist = library.getByIdOrName(Playlist, criteria)
+                if (!playlist) {
+                    printLongMessage("No playlist matches '${criteria}'.")
+                    return null }
+                return library.removeAllFromPlaylist(playlist.id)
+            case 'selection':
             default:
                 printLongMessage("Unrecognized option to the ${promptStyle}" +
-                    "add${normalStyle} command. Use ${promptStyle}help add" +
+                    "add${normalStyle} command. Use ${promptStyle}help clear" +
                     "${normalStyle} to see a list of valid options.")
                 return null
         }