List supported VCS for `arc backout`
List supported VCS for `arc backout`

Summary: This workflow does not work on subversion.

Test Plan: N/A

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D11625

wikimedia/phabricator-arcanist,aik099/arcanist,hach-que/arcanist,chundongwang/arcanist,folsom-labs/arcanist,wxstars/arcanist,folsom-labs/arcanist,sneakpeeq/arcanist,calblueprint/arcanist,haskell-infra/arcanist,alexmv/arcanist,zhihu/arcanist,phacility/arcanist,haskell-infra/arcanist,calblueprint/arcanist,memsql/arcanist,KieranHayes/arcanist,wharris/arcanist,folsom-labs/arcanist,memsql/arcanist,haskell-infra/arcanist,wxstars/arcanist,kevinseelbach/arcanist,hach-que/arcanist,coursera/arcanist,memsql/arcanist,r4nt/arcanist,uber/arcanist,fivestars/arcanist,codelabs-ch/arcanist,hach-que/arcanist,wharris/arcanist,KieranHayes/arcanist,wikimedia/phabricator-arcanist,memsql/arcanist,phacility/arcanist,chundongwang/arcanist,r4nt/arcanist,KieranHayes/arcanist,jra3/arcanist,eSpark/arcanist,haskell-infra/arcanist,wharris/arcanist,wharris/arcanist,aik099/arcanist,uber/arcanist,alexmv/arcanist,wikimedia/phabricator-arcanist,codelabs-ch/arcanist,Symplicity/arcanist,fivestars/arcanist,alexmv/arcanist,fivestars/arcanist,kevinseelbach/arcanist,uber/arcanist,calblueprint/arcanist,Symplicity/arcanist,sneakpeeq/arcanist,PageUpPeopleOrg/arcanist-patches,folsom-labs/arcanist,eSpark/arcanist,zhihu/arcanist,phacility/arcanist,phacility/arcanist,jra3/arcanist,zhihu/arcanist,Khan/arcanist,Khan/arcanist,Symplicity/arcanist,PageUpPeopleOrg/arcanist-patches,sneakpeeq/arcanist,PageUpPeopleOrg/arcanist-patches,kevinseelbach/arcanist,wxstars/arcanist,Khan/arcanist,KieranHayes/arcanist,alexmv/arcanist,codelabs-ch/arcanist,hach-que/arcanist,uber/arcanist,aik099/arcanist,zhihu/arcanist,kevinseelbach/arcanist,aik099/arcanist,jra3/arcanist,wxstars/arcanist,jra3/arcanist,calblueprint/arcanist,eSpark/arcanist,chundongwang/arcanist,sneakpeeq/arcanist,coursera/arcanist,coursera/arcanist,r4nt/arcanist,wikimedia/phabricator-arcanist,chundongwang/arcanist,Symplicity/arcanist,codelabs-ch/arcanist,PageUpPeopleOrg/arcanist-patches,fivestars/arcanist,eSpark/arcanist,codelabs-ch/arcanist,coursera/arcanist,r4nt/arcanist,phacility/arcanist,Khan/arcanist