Some forms of authors don't round-trip
Created originally on Bitbucket by glandium (Mike Hommey)
See the following reduced testcase:
#!shell $ mkdir a b $ cd b $ git init --bare $ cd ../a $ hg init $ echo a > a $ hg commit -A -m a -u foo@bar $ hg push ../b $ cd .. $ hg clone b c
The changeset in c doesn't have the same sha1 as the one in a because the author changed from
foo@bar <foo@bar>. Reading the code, there are likely other forms that don't round-trip.