tests/test-hgk.t

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.

Minimal hgk check

  $ echo "[extensions]" >> $HGRCPATH
  $ echo "hgk=" >> $HGRCPATH
  $ hg init repo
  $ cd repo
  $ echo a > a
  $ hg ci -Am adda
  adding a
  $ hg debug-cat-file commit 0
  tree a0c8bcbbb45c
  parent 000000000000
  author test 0 0
  revision 0
  branch default
  
  adda

  $ cd ..