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....
Also, GitHub PRs atleast to me feel like they encourage reviewing changes by the total diff of the entire PR, and not each commit. I don’t want a slog of commits that don’t add any value - it just makes doing things like reverts more annoying. Stuff like Gerrit and phabricator enforce reviews by making you review individual commits / changes / whatever you want to call them and not branch diffs.
Firefox Development Is Moving From Mercurial To Git (groups.google.com)
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....