revlog: allow reverse iteration with revlog.revs
We often need to perform rev iteration in reverse order. This
changeset makes it possible to do so, in order to avoid costly reverse
or reversed() calls later.
$ check_code="$TESTDIR"/../contrib/check-code.py
$ cd "$TESTDIR"/..
$ if hg identify -q > /dev/null; then :
> else
> echo "skipped: not a Mercurial working dir" >&2
> exit 80
> fi
$ hg manifest | xargs "$check_code" || echo 'FAILURE IS NOT AN OPTION!!!'
$ hg manifest | xargs "$check_code" --warnings --nolineno --per-file=0 || true