This depends on info in Revision and Build entities to calculate - I will work on this.

Oops, I didn't see this was for swarmbucket. I want to calculate this on the milo side. Is there a reason we need this in buildbucket?

In general, buildbot and buildbucket supports a list of change per build, where a change includes person email, revision, revision link, etc. This bug is scopes to "blamelist" property.

Currently swarmbucket has information about change, but does not set list of emails to blamelist property. This needs to be fixed. A blamelist property is enough for now, I think. I am not sure people pay attention to "changes" displayed on buildbot build page below steps.

Are the list of changes provided by the client to buildbucket? luci-cron won't have access to the previous builds and won't be able to calculate the list. If buildbucket can calculate it that sounds fine.

I was mostly concerned about tryjobs, buildbucket has change information for tryjob builds.

If we implement CI builds as a cron job, then buildbucket won't have information  about changes indeed. I guess we won't have blamelist in that case. When we implement CI builds as gitiles poller/listener in (future) scheduling service, the change information will be present.

Let's scope this bug to tryjobs.

sgtm

The following revision refers to this bug:
  https://chromium.googlesource.com/infra/infra.git/+/3df91a50eede9cafd7011f1b6bc6b7833d5b6ef8

commit 3df91a50eede9cafd7011f1b6bc6b7833d5b6ef8
Author: nodir <nodir@chromium.org>
Date: Tue Jun 07 22:42:01 2016

swarmbucket: add support for blamelist

Convert "changes" build parameter in format supported by
Buildbot-Buildbucket integration to "blamelist" build property in format
supported by Buildbot (list of emails) and expected by recipes

R=estaab@chromium.org, vadimsh@chromium.org
BUG= 613574 

Review-Url: https://codereview.chromium.org/2044253002

[modify] https://crrev.com/3df91a50eede9cafd7011f1b6bc6b7833d5b6ef8/appengine/cr-buildbucket/swarming/swarming.py
[modify] https://crrev.com/3df91a50eede9cafd7011f1b6bc6b7833d5b6ef8/appengine/cr-buildbucket/swarming/test/swarming_test.py