macOS' /usr/bin/patch and GNU patch have very subtle incompatibilities
that cause only some "more advanced" tests to fail in obscure and very
time-consuming ways - while other tests pass. In some cases (depending
on test threads racing), the lack of newlines in some test data even
causes the whole test suite to stall.
This fix runs `patch -version` (only once), makes sure the output starts
with "GNU patch" and shows a meaningful assert message when not. It also
looks for `gpatch` instead of `patch` on macOS and shows a meaningful
assert message if either is missing.
Fixes: #225
This also provides faster and better feedback when `ed` is missing (see
#39) and implements a portable and basic check.
Last but not least, this new code is generic enough to support the
validation of any other test dependency in the future.
* Implement -q/--brief option
* Optimization: stop analyzing the files as soon as there are any differences
* Unit tests for the stop_early parameter
* Simplify checks
Marc Herbert
Daniel Hofstetter
Sylvestre Ledru
Olivier Tilloy