Update to JLab 4, fix several issues with git sha ordering in git python, add support for diffing

[timkpaine]

fixes #123 fixes #112 fixes #105 starts on #42

[github-actions[bot]]

Test Results

6 tests  +2   6 :white_check_mark: +2   27s :stopwatch: +27s 3 suites +2   0 :zzz: ±0  2 files   +1   0 :x: ±0 

Results for commit e61e1f92. ± Comparison against base commit 79ed21ad.