command/playlist: allow range in playlistdelete

src/PlaylistFile.cxx

@@ -26,6 +26,7 @@
 #include "song/DetachedSong.hxx"
 #include "SongLoader.hxx"
 #include "Mapper.hxx"
+#include "protocol/RangeArg.hxx"
 #include "fs/io/TextFile.hxx"
 #include "fs/io/FileOutputStream.hxx"
 #include "fs/io/BufferedOutputStream.hxx"
@@ -314,6 +315,16 @@ PlaylistFileEditor::RemoveIndex(unsigned i)
 	contents.erase(std::next(contents.begin(), i));
 }
 
+void
+PlaylistFileEditor::RemoveRange(RangeArg range)
+{
+	if (!range.CheckClip(size()))
+		throw PlaylistError::BadRange();
+
+	contents.erase(std::next(contents.begin(), range.start),
+		       std::next(contents.begin(), range.end));
+}
+
 void
 PlaylistFileEditor::Save()
 {