Allow organization owners to use the Automatic Rebase workflow (#9090)

* Allow org owners to kick off automatic rebase

I suspect without this change PBJ couldn't kick off the automatic rebase
workflow.

This also includes a tweak to our method for determining if this is a
comment on a PR. I personally think this method is more explicit and
therefore readable.

* Add explanatory comment to rebase workflow

This might help someone determine what the workflow does at a glance, it
also documents a slightly unexpected caveat: The workflow can't be
triggered if your organization membership is private.

* Trigger Travis

Co-authored-by: rhymes <rhymesete@gmail.com>

.github/workflows/rebase.yml

@@ -1,4 +1,9 @@
-# https://github.com/marketplace/actions/automatic-rebase  (https://github.com/cirrus-actions/rebase)
+# This workflow allows an organization member or owner to kickoff an automated
+# rebase by commenting on a pull request with "/rebase". In order for the
+# workflow to run, organization membership must be set to public!
+
+# https://github.com/marketplace/actions/automatic-rebase (https://github.com/cirrus-actions/rebase)
+
 on:
   issue_comment:
     types: [created]
@@ -6,7 +11,10 @@ name: Automatic Rebase
 jobs:
   rebase:
     name: Rebase
-    if: github.event.issue.pull_request != '' && startsWith(github.event.comment.body, '/rebase') && github.event.comment.author_association == 'MEMBER'
+    if: contains(github.event.comment.html_url, '/pull/') &&
+      startsWith(github.event.comment.body, '/rebase') &&
+      (github.event.comment.author_association == 'MEMBER' ||
+      github.event.comment.author_association == 'OWNER')
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@master