Taskcluster/Deprecated/Operations/How-To/Enable a new Gecko Branch
Set up Branch Role
Figure out the branch's scm level. Here 'branch' is the path on hg.mozilla.org, and later 'shortbranch' is the last component of that name (e.g., project/ash and ash, respectively)
ssh hg.mozilla.org repo-group <branch>
then create the role using https://github.com/taskcluster/taskcluster-admin.
tcadmin make-gecko-branch-role <branch> <short-branch> <level>
Set up Mozilla-TaskCluster Configuration
Land a patch similar to https://github.com/taskcluster/mozilla-taskcluster/pull/61/files naming your newly created role and the level. Land and deploy the change.
Prime the tc-vcs cache
Land a patch similar to https://github.com/taskcluster/taskcluster-vcs/pull/62/files and wait for the hook to run.
Set up mozilla-taskcluster repo information
Login to the heroku console and navigate to the mozilla-taskcluster application. Click the "Compose MongoDB" button, click "repositories", and search for the repo by shortname, e.g., find({alias: "autoland"}).limit(10). If you don't find anything, you'll need to re-run the repository importer; otherwise, verify that the push ID in Mongo corresponds to the latest push ID in the hg repository. If Mongo has a push ID that is too high (which happens when a repo is reset), set it to the push ID in hg.