If a revision depends on another revision which has not yet been closed, warn the developer
If a revision depends on another revision which has not yet been closed, warn the developer

Summary: Have arc land inspect the revision if it depends on some other revisions which haven't been closed yet. If yes, then warn users.

Test Plan: Will test them locally.

Reviewers: epriestley, AnhNhan

CC: aran, Korvin, AnhNhan

Differential Revision: https://secure.phabricator.com/D5262

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