Show build results in `arc land`
Show build results in `arc land`

Summary:
Fixes T4809. When landing a revision, check for a (non-manual) buildable of the current diff. If we find one, check its status:

  - If it passed, print out a message to inform the user that we checked.
  - If it failed or is still building, print out details about the issue and require a confirmation to continue.
  - Just ignore other cases.

Test Plan:
  - Ran `arc land` on a revision with no buildable, a passing buildable, a failed buildable, and a building buildable for the current diff.
  - Got sensible output / prompts.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T4809

Differential Revision: https://secure.phabricator.com/D8801

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