tests/test-gendoc-zh_TW.t

test-grep: add tests for --follow with/without --diff and/or paths

This tests the behavior of cmdutil.walkchangerevs().

I'm going to rewrite cmdutil.walkchangerevs() to leverage the "log -f"
logic, but the code coverage looked quite small. And the history traversal
of "grep -f" goes wrong in various ways.

#require docutils gettext

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