http://hg-git.github.com/
> This is the Hg-Git plugin for Mercurial, adding the ability to *push to and pull from a Git server* repository from Mercurial. This means you can collaborate on Git based projects from Mercurial, or use a Git server as a collaboration point for a team with developers using both Git and Mercurial
> The Hg-Git plugin can *convert commits/changesets losslessly* from one system to another, so you can push via a Mercurial repository and another Mercurial client can pull it. In theory, the changeset IDs should not change
Ну прямо философский камень какой–то