tree fc1dd7e694b39a14dda8236d0561e0bb78bc5154
parent 514db293af344e15d7a1f1585c2ac84c3694eb0f
author Evgeny Antyshev <eantyshev@virtuozzo.com> 1453733061 +0000
committer Evgeny Antyshev <eantyshev@virtuozzo.com> 1453733740 +0000

Don't require 'commit' attribute in merge event

Problem occurs when merge events for periodic pipeline
are processed: first, a trivial mistake in type checking
introduced in review 243493,
second, merge events generated for NullChange's are repo updates,
and don't provide 'commit' attribute.
I don't see the necessity to enforce 'build_set.commit' to be set
(which is given to job env ZUUL_COMMIT if 'ref' or 'refspec' are set,
but that's not the case for NullChange)

Change-Id: Ib5da4ba987898d37d8e5082f4b8e2a5c31910323