Make --auto creates actually work in SVN and HG
Make --auto creates actually work in SVN and HG

Summary:
--auto doesn't work right now on the implicit --create pathway in SVN and HG because we hit these conditions.

Also improve a message.

Test Plan: Ran "arc diff" in unaffiliated working copies in HG and SVN.

Reviewers: svemir, btrahan, vrana, jungejason

Reviewed By: svemir

CC: aran

Differential Revision: https://secure.phabricator.com/D2187

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