Merge branch 'tc/last-modified-options-cleanup' into seen

The "-z" and "--max-depth" documentation (and implementation of
"-z") in the "git last-modified" command have been updated.

* tc/last-modified-options-cleanup:
  last-modified: change default max-depth to 0
  last-modified: add option '--max-depth' to help output
  last-modified: document option --max-depth
  last-modified: add option '-z' to help output
  last-modified: document NUL termination

diff --cc builtin/last-modified.c
Simple merge

diff --cc t/t8020-last-modified.sh
Simple merge