Open Stack

Hi,

Earlier[1][2], we discussed proposals to make files and irrelevant-files
easier to use -- particularly ways to make them overridable.  We settled
on an approach, and it is now implemented.  We plan on upgrading
OpenStack's Zuul to the new behavior on Monday, June 11, 2018.

To summarize the change:

  Files and irrelevant-files are treated as overwriteable attributes and
  evaluated after branch-matching variants are combined.
  
  * Files and irrelevant-files are overwritten, so the last value
    encountered when combining all the matching variants (looking only at
    branches) wins.
  * It's possible to both reduce and expand the scope of jobs, but the
    user may need to manually copy values from a parent or other variant
    in order to do so.
  * It will no longer be possible to alter a job attribute by adding a
    variant with only a files matcher -- in all cases files and
    irrelevant-files are used solely to determine whether the job is run,
    not to determine whether to apply a variant.

This is a behavior change to Zuul that is not possible[3] to support in
a backwards compatible way.  That means that on Monday, there may be
sudden alterations to the set of jobs which run on changes.  Considering
that many of us can barely predict what happens at all when multiple
irrelevant-files stanzas enter the picture, it's not possible[4] to say
in advance exactly what the changes will be.

Suffice it to say that, on Monday, if some jobs you were expecting to
run on a change don't, or some jobs you were not expecting to run do,
then you will need to alter the files or irrelevant-files matchers on
those jobs.  Hopefully the new approach is sufficiently intuitive that
corrective changes will be simple to make.  Jobs which have no more than
one files or irrelevant-files attribute involved in their construction
(likely the bulk of the jobs out there) are unlikely to need any
immediate changes.

Please let us know in #openstack-infra if you encounter any problems and
we'll be happy to help.  Hopefully after we cross this speedbump we'll
find the files and irrelevant-files matchers much more useful.

-Jim

[1] http://lists.openstack.org/pipermail/openstack-dev/2018-May/130074.html
[2] http://lists.zuul-ci.org/pipermail/zuul-discuss/2018-May/000397.html
[3] At least, not possible with a reasonable amount of effort.
[4] Of course it's possible but only with an unhealthy amount of beer.