Firefox Git Migration Update

Apr 2025

We are migrating the source of truth for Firefox from Mercurial to Git - see the previous Firefox Git Migration Update for more details.

Timeline

Starting on the 30th April at 12:30pm UTC (8:30am US/Eastern) we will commence the migration.

The trees will be closed, Phabricator and Lando will be offline.

If all goes to plan we expect the migration to take no more than two hours.

What to Expect

• An outage followed by business as usual for most engineers
• Pushing to try from the new Git repository must happen via Lando

Action Required

• No action is required on migration day
• To ensure full functionality make sure you're running the latest version of moz-phab, version 1.8.1 run moz-phab self-update
• Plan to migrate your local repository to Git as soon as is viable; we recommend coordinating your migration with other engineers you work closely with

Workstation Migration

Your local work will need to be migrated from a hg/git-cinnabar clone of Mercurial's repository to a vanilla Git clone from GitHub after we have migrated the infrastructure.

The simplest option, and the one we recommend for most users, is to move commits on an as-required basis:

1. Clone the firefox repository: git clone https://github.com/mozilla-firefox/firefox.git

• You can add --depth 1 to the command for a faster clone that excludes the complete history

2. Export commits from your existing repository

• Use hg export or git format-patch

3. Apply the patch(es) to the new git repository

• For most this will likely involve creating a new branch then using git am or git apply to apply the patches

gecko-dev

The current GitHub mirror of mozilla-central - https://github.com/mozilla/gecko-dev/ - will continue to operate for at least a month after the migration.

At some point we will archive gecko-dev and decommission the service that is keeping it up-to-date.

Repository Map

Questions?

Join #hg-to-git on Mozilla Slack.