The complete list of event "actions" emitted by GitHub (and recognized
by Taskcluster) is [1]:

> - assigned
> - unassigned
> - labeled
> - unlabeled
> - opened
> - edited
> - closed
> - reopened
> - synchronize
> - review_requested
> - review_request_removed

Most of these have no bearing on the code under review, so they should
not trigger validation.

Do not validate commits in response to irrelevant events.

[1] https://docs.taskcluster.net/docs/reference/integrations/taskcluster-github/references/events