Merge branch 'jc/name-rev-stdin'

Using "git name-rev --stdin" as an example, improve the framework to prepare tests to pretend to be in the future where the breaking changes have already happened. * jc/name-rev-stdin: name-rev: remove "--stdin" support t6120: further modernize t6120: avoid hiding "git" exit status t: introduce WITH_BREAKING_CHANGES prerequisite t: extend test_lazy_prereq t: document test_lazy_prereq