Merge branch 'jc/clean' into next

* jc/clean:
  Teach git-clean optional <paths>... parameters.
  Separate object name errors from usage errors
  Documentation: {caret} fixes (git-rev-list.txt)
  Fix "git diff --stat" with long filenames
  Fix repo-config set-multivar error return path.

diff --cc diff.c
Simple merge

diff --cc read-tree.c
Simple merge