#1302: Add new git_clone_missing rule

* Add git clone missing rule

* Clean up tests and improve matching

* Make rules behave correctly?

* Improve tests and redo matcher

* Remove unnecessary tests

* Improvements as per code review

* Remove dead tests

* Improve match function for git clone missing

* Improve tests

* Fix more tests

* Fix failing test

* Add Macos's /bin/sh command output to match

* Add output for lines uncovered by tests

Co-authored-by: Pablo Santiago Blum de Aguiar <scorphus@gmail.com>