Merge branch 'as/t4012-style-updates'

* as/t4012-style-updates:
  t4012: Use test_must_fail instead of if-else
  t4012: use 'printf' instead of 'dd' to generate a binary file
  t4012: Re-indent test snippets
  t4012: Make --shortstat test more robust
  t4012: Break up pipe into serial redirections
  t4012: Actually quote the sed script
  t4012: Unquote git command fragment in test title
  t4012: modernize style for quoting