changelog: lazily parse description Before, the description field was converted to a localstr at parse time. With this patch, we store the raw description and convert to a localstr when it is first accessed. We see a revset speedup for revsets that don't access the description: author(mpm) 0.896565 0.914234 0.869085 date(2015) 0.878797 0.891980 0.862525 extra(rebase_source) 0.865446 0.912514 0.871500 author(mpm) or author(greg) 1.801832 1.860402 1.791589 date(2015) or branch(default) 0.968276 0.994673 0.974027 author(mpm) or desc(bug) or date(2015) or extra(rebase_source) 3.656193 3.721032 3.643593 As you can see, most of these revsets are already faster than from before this refactoring: we have already offset the performance loss from the introduction of the new class representing parsed changelog entries!