Firefox 宣佈從 Mercurial 換到 Git：「Firefox Development Is Moving From Mercurial To Git」。
目前是 Mercurial 與 Git 都支援，理由是不想要維持兩套：
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.
不過不知道決策的過程到底是怎麼產生的，算是 Mozilla 的老問題了...