Personally, I don’t like to do resets on hg. Git resets are so much easier.
B2G happens to be a mirror off of git.mozilla.org so it works off of git.
Unfortunately, gecko devs work off of hg.
So in order to find the same revision you have to either have a mapping or I found an easier way: git log –grep=”Bug 1107139″
or whatever bug you’re looking up.
Both gecko and gaia dev have a work flow that includes the bug number. This will show you all the revs with that bug number.
You can then do a: git reset –hard d103771dfdee3f8475a10f3de9ff5998ac2d686e
or whatever your hash you want to reset is.
On hg, installing extensions helps out a lot in terms of backout and such…. still got a bit to learn about how hg works.
[edit: If you want to try reset on hg, there’s some reading material… http://stackoverflow.com/questions/2672454/how-do-i-git-reset-hard-head-on-mercurial ]