Summary:
This uses a similiar approach as with postponed unittests, allowing
the lint workflow/engine to report postponed linter names. After
the lint engine is run, a separate method is used to collect any
postponed linters and these are reposted to the diff via the
"arc:lint-postponed" property.
Also, a ##diff.wasCreated## was added allowing hooks to be called
immediately after the call ##differential.creatediff## with the
returned diff ID.
Test Plan:
Created diffs with a dummy lint engine which always reports a
postponed linter.
Reviewers: epriestley, vrana
Reviewed By: epriestley
CC: aran, Korvin
Maniphest Tasks: T1332
Differential Revision: https://secure.phabricator.com/D2933