Merge branch 'js/range-diff-wo-dotdot'

Merge branch 'js/range-diff-wo-dotdot'

There are other ways than ".." for a single token to denote a
"commit range", namely "<rev>^!" and "<rev>^-<n>", but "git
range-diff" did not understand them.

* js/range-diff-wo-dotdot:
  range-diff(docs): explain how to specify commit ranges
  range-diff/format-patch: handle commit ranges other than A..B
  range-diff/format-patch: refactor check for commit range