diff: re-establish linear runtime performance The previous method with sum() and list() creates a new list object for every hunk. Then sum() is used to flatten out this sequence of lists. The sum() function is not "lazy", but creates a new list object for every "+" operation and so this code had quadratic runtime behaviour.

To run the tests, do:

cd tests/
python run-tests.py

See https://mercurial-scm.org/wiki/WritingTests for
more information on writing tests.