Simplify test stragety

[MitchellThompkins]

Description

#32 added a CI environment but did so in a very hacky way that I was unhappy with basically immediately. It did let me test test both locally and in CI but by doing some non-ideal searching through files to aggregate all the test files.

This was all in an effort to avoid installing the control package in the docker container because install in the Makefile depends on dist, which depends on docs and the docker image I was using from https://github.com/gnu-octave/docker lacked the tooling to actually build the docs (FWIW I think https://github.com/gnu-octave/octave-buildbot does have the tooling but I don't believe actually builds octave itself and therefore can't be used for testing).

I realized I could just copy the installation makefile recipe and strip out the docs generation stuff. That combined with the fact that I realized __run_test_suite__ existed let me drastically reduce the complexity of the CI environment. It also makes the output much more legible. See the standard octave test results vs what I was doing before (both of those produce 389 tests, but the new version is way cleaner).

The only trade-off is that installation uses git archive which means that for a file to be tested it has to be tracked by git. For files that are already tracked by git I've used git stash create to temporarily grab the hash that would be represented if you were to make the commit. However files that are completely untracked (so new files) won't be picked up at all, so you need to git add them in order to actually test. The trade-off for simplicity seems acceptable to me. I've updated the CONTRIBUTION.md to reflect this as well.

Changes

• Minor copy/paste changes to makefile to copy existing installation recipe
• Drastically reduces the complexity of the script used to run tests
• Updates local test contribution guidelines