The current official git mirror of mozilla-central can be found at https://github.com/mozilla/gecko-dev. If you are looking to work with other Mozilla branches, https://github.com/mozilla/gecko-projects might also be of use. There is also an etherpad which attempts to describe how to use git to interact with mozilla-central.
For historical reference, the rest of this page describes how you could maintain your own mirror - but almost everyone should be able to use the URL above.
Maintaining your own Mercurial mirror of mozilla-central
The rest of this page is for historical reference only - most people can ignore it and it's almost certainly out of date - refer to the information above.
The most commonly used Mercurial mirror is at https://github.com/doublec/mozilla-central
This repository is synced using hg-git. The git-mapfile for it is available at http://www.bluishcoder.co.nz/git-mapfile.bz2
Bootstrapping a hg-git repo
hg clone http://hg.mozilla.org/mozilla-central mozilla-central-hg-git
cd mozilla-central-hg-git/.hg
wget http://www.bluishcoder.co.nz/git-mapfile.bz2
bunzip2 git-mapfile.bz2
git clone git://github.com/doublec/mozilla-central.git --bare git
cd ../
# sync up what's left
hg gexport
Misc
-R can be used for specifying a repository other than nearest .hg
e.g. hg -R ../mozilla-central-hg-git push .
Things that would be nice to be able to do
use try-server