tests/test-extra-filelog-entry.t

revlog: simplify entry update logic in `rewrite_sidedata`

We don't need to rebuild the full entry. So lets just gather the data we need
to pass to `replace_sidedata_info`.

Differential Revision: https://phab.mercurial-scm.org/D10642

Issue351: mq: qrefresh can create extra revlog entry

  $ echo "[extensions]" >> $HGRCPATH
  $ echo "mq=" >> $HGRCPATH

  $ hg init
  $ hg qinit

  $ echo b > b
  $ hg ci -A -m foo
  adding b

  $ echo cc > b
  $ hg qnew -f foo.diff
  $ echo b > b
  $ hg qrefresh

  $ hg debugindex b
     rev linkrev nodeid       p1           p2
       0       0 1e88685f5dde 000000000000 000000000000