tests: replace mockmakedate function in test-amend.t
This is a follow up patch for D5554. This replaces mockmakedate function
by `tests/mockmakedate.py`.
Differential Revision: https://phab.mercurial-scm.org/D5577
To run the tests, do:
cd tests/
python run-tests.py
See https://mercurial-scm.org/wiki/WritingTests for
more information on writing tests.