convert: use a priority queue for sorting commits, to make sorting faster To achieve this, we turn commit sorters into classes so they can encapsulate state. This reduces the sorting time from ~30s to ~10s on a 500k-commit prefix of a repo I tried to convert. (and probably reduces the time to sort the whole repo from many tens of minutes to minutes, but I didn't try that again) The date caching gets removed because priority queue already caches the key.

https://bz.mercurial-scm.org/1089

  $ hg init repo
  $ cd repo
  $ mkdir a
  $ echo a > a/b
  $ hg ci -Am m
  adding a/b

  $ hg rm a
  removing a/b
  $ hg ci -m m a

  $ mkdir a b
  $ echo a > a/b
  $ hg ci -Am m
  adding a/b

  $ hg rm a
  removing a/b
  $ cd b

Relative delete:

  $ hg ci -m m ../a

  $ cd ..