Just mirroring the solution I found here to find it later on.

How to make patch with git and with mercurial

git log
git log HEAD^ -p
git format-patch HEAD^
git send-email 001-patchname.patch
git send-email HEAD^ # alternatively

Doing the same w/ HG:

hg log # note this isn't paginated, a feature git has over hg imo
hg log -r tip -p
hg email -r tip