The reports of Thunderbird's death have been greatly exaggerated.

Merge Day Automation


Merge day happens at 4-week intervals (most of the time), and follows the Firefox Rapid Release schedule. This document only covers merge activities, not the related releases that happen on the same day.

On Merge day:

  • Communication about the merges
  • Merge comm-central to comm-beta
  • Tag and bump comm-central versions
  • Update ShipIt nightly version


Send emails to the thunderbird-drivers list with information about the merge and status updates. Templates are here


Make sure you are logged into Treeherder. You will need to have "thunderbird-releng" permissions, which are set in Taskcluster.

Close the trees in TreeStatus.

comm-central -> comm-beta

  1. In Treeherder, select the comm-central repository
  2. Select the Decision task of the latest push
  3. Click the down arrow in the top right corner and select "Custom push action..."
  4. Choose "merge-automation"
  5. Update the payload & trigger (note that with force-dry-run set to true, the value of push is ignored)
behavior: comm-central-to-beta
force-dry-run: true
push: true

If the dry-run is successful, run it again, this time setting force-dry-run to false.

Update .gecko_rev.yml

The automation will pin to mozilla-beta@default. This will build. A specific revision needs to be pinned manually before releasing beta 1.

Suite version

The automation will change 2.XXa1 to 2.XXb1.

Bump Daily version

  1. Select comm-central repository in Treeherder and select the "merge-automation" custom action as above
  2. Update the payload & trigger
behavior: comm-bump-central
force-dry-run: true
push: true

If the dry-run is successful, run again without force-dry-run.

Manual step: bump suite version

This requires a local clone of comm-central. Run this after the above pushes to comm-central.

  1. Edit suite/config/version.txt and version_display.txt Increment the minor number in each by 1. The files should be identical when complete.
  2. Commit: "No bug - Bump suite versions. r=me a=merge CLOSED TREE DONTBUILD"
  3. Push to comm-central.

Update Ship-It

Mozilla's Ship-It tool must be updated with the new Daily version number.


  • Modify api/src/shipit_api/common/ and update the LATEST_THUNDERBIRD_NIGHTLY_VERSION variable to be the new version of comm-central.
  • Create a pull request with the changes. Example
  • In the pull request, @mention one of the Ship-It code owners to make sure the request is seen. You can also say something in #releaseduty on Matrix.

If you are not familiar with Github's Fork & Pull workflow model, see here for an introduction.

Test runs with a real push

You can push to try-comm-central with to-repo/from-repo to test that pushing actually works, though it really shouldn't break now that it's working.

to-repo, from-repo, to-branch, from-branch?

It's kind of confusing...

  • to-branch and from-branch are Firefoxtree "branch" names, and correspond to "branches" of code for release purposes
  • to-repo in a merge context is the URL of the destination repository you want to merge into. So for comm-central-to-beta, that's the full URL (https) of comm-beta on hg.m.o.
  • from-repo then is the repo URL you are merging into to-repo. So, comm-central's URL.
  • VERY IMPORTANT Merge day work will push to both to-repo and from-repo. So if you are testing push stuff, make sure to set both to try-comm-central's URL.