This checks combinations of i18n.commitencoding (declares what
encoding you are feeding commit-tree to make commits) and
i18n.logoutputencoding (instructs what encoding to emit the
commit message out to log output, including e-mail format) to
make sure the "format-patch | am" pipe used in git-rebase works
correctly.
I suspect "git cherry-pick" and "git rebase --merge" may fail
similar tests. We'll see.