hg clone ssh://hg@bitbucket.org/owner/repo
Now we'll need Git-Hg (massive kudos to offbytwo for making it possible):
git clone git://github.com/offbytwo/git-hg.git cd git-hg/ git submodule update --init fast-export cd ../repo ../git-hg/bin/git-hg clone ssh://hg@bitbucket.org/owner/repo touch .gitignore git add .gitignore git pull git+ssh://git@github.com/mdvcs/md.git
Here I had some problems with the git repository already having a README file, so I just removed it and proceeded with the push.
git rm README git push git+ssh://git@github.com/mdvcs/md.git
And you're done.