Replace varargs_callback in duplicates
Replace varargs_callback in duplicates

Now you just use `-k KEY1 -k KEY2`, which seems more natural to me anyway.

mosesfistos1/beetbox,xsteadfastx/beets,ibmibmibm/beets,pkess/beets,artemutin/beets,beetbox/beets,pkess/beets,mosesfistos1/beetbox,sampsyo/beets,beetbox/beets,sampsyo/beets,madmouser1/beets,lengtche/beets,xsteadfastx/beets,madmouser1/beets,artemutin/beets,ibmibmibm/beets,xsteadfastx/beets,xsteadfastx/beets,MyTunesFreeMusic/privacy-policy,diego-plan9/beets,MyTunesFreeMusic/privacy-policy,jackwilsdon/beets,SusannaMaria/beets,Kraymer/beets,beetbox/beets,sampsyo/beets,madmouser1/beets,SusannaMaria/beets,jackwilsdon/beets,shamangeorge/beets,artemutin/beets,MyTunesFreeMusic/privacy-policy,lengtche/beets,Kraymer/beets,sampsyo/beets,artemutin/beets,ibmibmibm/beets,shamangeorge/beets,Kraymer/beets,pkess/beets,shamangeorge/beets,diego-plan9/beets,diego-plan9/beets,Kraymer/beets,jackwilsdon/beets,beetbox/beets,lengtche/beets,mosesfistos1/beetbox,shamangeorge/beets,SusannaMaria/beets,SusannaMaria/beets,diego-plan9/beets,MyTunesFreeMusic/privacy-policy,ibmibmibm/beets,lengtche/beets,jackwilsdon/beets,madmouser1/beets,pkess/beets,mosesfistos1/beetbox