Merge branch 'md/test-cleanup'

Various test scripts have been updated for style and also correct handling of exit status of various commands. * md/test-cleanup: tests: order arguments to git-rev-list properly t9109: don't swallow Git errors upstream of pipes tests: don't swallow Git errors upstream of pipes t/*: fix ordering of expected/observed arguments tests: standardize pipe placement Documentation: add shell guidelines t/README: reformat Do, Don't, Keep in mind lists