Comment 37 for bug 219385

(In reply to comment #15)
> We don't know how to make changes to our local hg repository and stay
> synced with mozilla-central in the same time.

Getting the equivalent of git commit --amend is not quite trivial with mercurial.
Most people use the mq extension for this. It sounded a bit much effort to me, but, once I actually tried it, it wasn't so hard to learn.

https://developer.mozilla.org/en/Mercurial_Queues

This does come in very handy for separating projects into manageable-sized patches, particularly when each patch in the series is still under development.
The gtk2 plugin work at least should be separate from the base gtk3 patch (and perhaps could even be split into a number of smaller patches).

http://weblogs.mozillazine.org/roc/archives/2010/01/more_on_patch_d.html