add concurrent-output
add concurrent-output

git-annex would like to build using this library
nomeata/stackage,Gabriel439/stackage,simonmichael/stackage,creichert/stackage,mgajda/stackage,massysett/stackage,mrkkrp/stackage,l29ah/stackage,ygale/stackage,Shimuuar/stackage,marcinmrotek/stackage,meteficha/stackage,alanz/stackage,codedmart/stackage,fimad/stackage,mstksg/stackage,wereHamster/stackage,jonschoning/stackage,brendanhay/stackage,stackbuilders/stackage,k0ral/stackage,athanclark/stackage,phadej/stackage,soenkehahn/stackage,clinty/stackage,iand675/stackage,judah/stackage,GregorySchwartz/stackage,jaspervdj/stackage,asr/stackage,DanielG/stackage,michalkonecny/stackage,Daniel-Diaz/stackage,peti/stackage,bartavelle/stackage,spencerjanssen/stackage,int-index/stackage,christiaanb/stackage,garetxe/stackage,agrafix/stackage,lwm/stackage,fpco/stackage,phaazon/stackage,ethercrow/stackage