"git tbdiff" that lets us compare individual patches in two
iterations of a topic has been rewritten and made into a built-in
command.

* js/range-diff: (21 commits)
  range-diff: use dim/bold cues to improve dual color mode
  range-diff: make --dual-color the default mode
  range-diff: left-pad patch numbers
  completion: support `git range-diff`
  range-diff: populate the man page
  range-diff --dual-color: skip white-space warnings
  range-diff: offer to dual-color the diffs
  diff: add an internal option to dual-color diffs of diffs
  color: add the meta color GIT_COLOR_REVERSE
  range-diff: use color for the commit pairs
  range-diff: add tests
  range-diff: do not show "function names" in hunk headers
  range-diff: adjust the output of the commit pairs
  range-diff: suppress the diff headers
  range-diff: indent the diffs just like tbdiff
  range-diff: right-trim commit messages
  range-diff: also show the diff between patches
  range-diff: improve the order of the shown commits
  range-diff: first rudimentary implementation
  Introduce `range-diff` to compare iterations of a topic branch
  ...