Merge branch 'tb/cat-file-z'

Operating modes like "--batch" of "git cat-file" command learned to
take NUL-terminated input, instead of one-item-per-line.

* tb/cat-file-z:
  builtin/cat-file.c: support NUL-delimited input with `-z`
  t1006: extract --batch-command inputs to variables

diff --cc Documentation/git-cat-file.txt
Simple merge

diff --cc builtin/cat-file.c
Simple merge