Add option to disable PRIMARY notifications

[alexozer]

This can cut down on unnecessary notifications for clipmenud when told not to handle PRIMARY.

See this.

[cdown]

Hey there! Thanks for the contribution. I was thinking about doing this, but didn't get around to it yet, so thanks for that.

I'd rather, however, that we have a --selections/-s option, so that this could go either way -- disable primary or clipboard, or a clipboard generically.

[alexozer]

That makes sense! Plus that would match clipmenud's convention.

Or, maybe you could just call clipnotify like clipnotify clipboard or clipnotify primary clipboard which would make it easy to call from clipmenu too.

[cdown]

-s is in clipmenu 2.0 to select particular selections :-)