Log Message:
release 3.6:

** New features

  When one file is a prefix of the other, cmp now appends the shorter
  file's size to the EOF diagnostic.

** Bug fixes

  Using an invalid regular expression with --ignore-matching-lines=RE (-I)
  no longer causes stack overflow.  Before, with an invocation like the
  following, diff would diagnose the error, but would still proceed to
  blow the stack: diff -Ia -I\\ <(echo) <(echo b)
  [bug introduced in 2.9]

  diff no longer mishandles line numbers exceeding 2**31 on Mingw-w64.

  the ---presume-output-tty (ostensibly test-only) option would cause
  diff --color to read an uninitialized variable
  [bug introduced in 3.4]

** Performance changes

  diff's default algorithm has been tweaked to deal better with larger
  files, reversing some of the changes made in diffutils-3.4.