Merge branch 'ps/cat-file-null-output'

Merge branch 'ps/cat-file-null-output'

"git cat-file --batch" and friends learned "-Z" that uses NUL
delimiter for both input and output.

* ps/cat-file-null-output:
  cat-file: add option '-Z' that delimits input and output with NUL
  cat-file: simplify reading from standard input
  strbuf: provide CRLF-aware helper to read until a specified delimiter
  t1006: modernize test style to use `test_cmp`
  t1006: don't strip timestamps from expected results