Merge branch 'master' into next

Merge branch 'master' into next

* master:
  Clean up and simplify rev_compare_tree()
  blame: correctly handle a path that used to be a directory
  add -i: do not dump patch during application
  Update draft release notes for 1.6.3.2
  test-lib: fix http exit codes
  test-lib: allow exit trap to be used for cleanup by tests
  test-lib: fail if invalid options are passed
  grep: fix colouring of matches with zero length
  git-show-branch.txt: document --date-order option
  diff: generate pretty filenames in prep_temp_blob()
  compat: add a basename() compatibility function
  compat: add a mkstemps() compatibility function
  Documentation: teach stash/pop workflow instead of stash/apply
  Change xdl_merge to generate output even for null merges
  t6023: merge-file fails to output anything for a degenerate merge