tests/test-extra-filelog-entry.t

formatter: add helper to create a formatter optionally backed by file

To make things simple, openformatter() and maybereopen() have no support
for a plain object API. Callers must use the "with" statement.

Unlike cmdutil.makefileobj(), append mode ('ab') isn't supported by these
functions. This is because JSON output can't be simply concatenated. Perhaps
cmdutil.export() will have to build a {filename: [revs...]} map first and
write revs per file.

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    offset  length  ..... linkrev nodeid       p1           p2 (re)
       0         0       3  .....       0 1e88685f5dde 000000000000 000000000000 (re)