tree 148a67aea7dfc31871301852d3a4bb416cf3317b
parent 2b4890fa7c299c010ec47ae8441985fd4b530eea
author James E. Blair <jeblair@hp.com> 1420763128 -0800
committer James E. Blair <jeblair@hp.com> 1420763128 -0800

Cloner: handle missing ZUUL_BRANCH/_REF

Periodic jobs currently trigger without a ZUUL_BRANCH or ZUUL_REF
variable set.  (We should change this, but that's a more complex
change).

So that the cloner can be used in this situation, set those to
the empty string if their value is None (ie, unset).

Periodoc jobs can then invoke the cloner as normal, with branch
override values set, and those will be used as the selected
branch.  This is how OpenStack's periodic branch jobs currently
work.

In the future, if Zuul itself performs branch selection on jobs,
this will provide a graceful migration path by allowing the
ZUUL_BRANCH values to act as a fallback and then the overrides
can be removed.

Add a test to validate this usage.

Change-Id: Ie680b9c11cebec7410ef7b0edc9d1017ae8b847e