help: explain in `hg help flags` that unambiguous prefixes are allowed I used `hg commit --amend` as an example because that's the most frequently used flag I could think of that doesn't yet have a short form. Differential Revision: https://phab.mercurial-scm.org/D8607

git: add coverage for manifest.diff() so we don't regress

git: implement diff manifest method This makes 'hg diff' work.