Support running multiple tests per commit. e.g. `git test run -t build,lint,unittest main..mybranch`

[hlovdal]

These are changes I have been using locally for a long time, and would like to have applied upstream.

It resolves the majority of issue #12.

Commit "Add support for running multiple tests for each commit" is best reviewed with ignore space changes since it changes indentation level with for test in tests: for several lines.