Merge branch 'js/range-diff-diff-merges'

"git range-diff" learned to optionally show and compare merge
commits in the ranges being compared, with the --diff-merges
option.

* js/range-diff-diff-merges:
  range-diff: introduce the convenience option `--remerge-diff`
  range-diff: optionally include merge commits' diffs in the analysis

diff --cc builtin/range-diff.c
Simple merge

diff --cc range-diff.c
Simple merge

diff --cc t/t3206-range-diff.sh
Simple merge