For a long time Firefox Desktop development has supported both Mercurial and Git users. This dual SCM requirement places a significant burden on teams which
are already stretched thin in parts. We have made the decision to move Firefox
development to Git.
We will continue to use Bugzilla, moz-phab, Phabricator, and Lando
Although we'll be hosting the repository on GitHub, our contribution workflow will remain unchanged and we will not be accepting Pull Requests at this time
We're still working through the planning stages, but we're expecting at least six months before the migration begins
APPROACH
In order to deliver gains into the hands of our engineers as early as possible, the work will be split into two components: developer-facing first, followed by piecemeal migration of backend infrastructure.
Phase One - Developer Facing
We'll switch the primary repository from Mercurial to Git, at the same time removing support for Mercurial on developers' workstations. At this point you'll need to use Git locally, and will continue to use moz-phab to submit patches for review.
All changes will land on the Git repository, which will be unidirectionally synchronised into our existing Mercurial infrastructure.
Phase Two - Infrastructure
Respective teams will work on migrating infrastructure that sits atop Mercurial to Git. This will happen in an incremental manner rather than all at once.
By the end of this phase we will have completely removed support of Mercurial from our infrastructure.
Could be familiarity? I saw an article go by recently about how projects that aren't on GitHub suffer from lack of contributions. Although that matters more for smaller projects, Mozilla is a beast and could probably pull people off GitHub if it wanted to.
Also if anyone should be trying to build up an alternative to GitHub, it should be Mozilla
If you are at a skill level, where you can meaningfully contribute to a project like this, registering for an alternative git provider should not be an obstacle
It's super cool that it supports this, heck I've used it when no other options were there (and thank git I could! It made a nightmare into just a little more work instead).
I will say though, it's most of the other software forge features that people normally talk about adding Activity Pub support for (issues tracking, merge requests, tracking forks, CI tooling, handling documentation, etc).
It’s the most widely used platform that the most people are familiar with that they get to use likely for free. Newer projects of theirs are also hosted there. Why would you say it makes no sense?