tests/test-gendoc-zh_CN.t

upgrade: introduce a _copyrevlog method

This function copies a revlog from the old store to the new one, without
re-adding all deltas manually. This will eventually save a lot of time when some
revlog does not needs any conversions.

Code actually using this will be introduced in later changesets.

#require docutils gettext

  $ $TESTDIR/check-gendoc zh_CN
  checking for parse errors