https://git-scm.com/docs/git-checkout
https://www.mercurial-scm.org/repo/hg/help/update
https://www.mercurial-scm.org/repo/hg/help/revert
https://git-scm.com/docs/git-checkout
https://www.mercurial-scm.org/repo/hg/help/update
https://www.mercurial-scm.org/repo/hg/help/revert