For 100 items, this change improves generation times on small diffs
(100s of bytes) 6-fold. The improvement deteriorates to about 4-fold on
diffs of 1kB.
This includes the 25% improvement from the removal of unnecessary
forTemplate calls - we pack the diffs into HTMLText and render them
later from a template anyway.
Deprecate the getDiffedChanges method to get rid of confusing
fullHistory parameter. Add a getDiff method to fetch just a single diff
and a more versatile getDiffList method which allows specifying a limit.
We now also cap the amount of items coming from the diffing process
to a default value that we hope will result in generation times no
greater than a few seconds. This can be reconfigured by developers.
