tests/test-gendoc-da.t

rebase: don't call rewriteutil.precheck() with to-be-skipped commits

It's clearly incorrect to call `rewriteutil.precheck()` for commits
that we're not about to rewrite. We haven't noticed yet because the
function doesn't check for divergence, but I'm about to teach it to do
that.

Differential Revision: https://phab.mercurial-scm.org/D10259

#require docutils gettext

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