changelog: lazily parse date/extra field This is probably the most complicated patch in the parsing refactor. Because the date and extras are encoded in the same field, we stuff the entire field into a dedicated variable and add a property for accessing the sub-components of each. There is some duplicated code here. But the code is relatively simple, so it shouldn't be a big deal. We see revset performance wins across the board: author(mpm) 0.896565 0.876713 0.822961 desc(bug) 0.887169 0.895514 0.847054 date(2015) 0.878797 0.820987 0.811613 extra(rebase_source) 0.865446 0.823811 0.797756 author(mpm) or author(greg) 1.801832 1.784160 1.668172 author(mpm) or desc(bug) 1.812438 1.822756 1.677608 date(2015) or branch(default) 0.968276 0.910981 0.896032 author(mpm) or desc(bug) or date(2015) or extra(rebase_source) 3.656193 3.516788 3.265024 We see a speed-up on revsets accessing date and extras because the new parsing code only parses what you access. Even though they are stored the same text field, we avoid parsing dates when accessing extras and vice-versa. But strangely revsets accessing both date and extras appeared to speed up as well! I'm not sure if this is due to refactoring the parsing code or due to an optimization in revsets. You can't argue with the results!