Baptiste Daroussin f096ed981f Restore compatibility with GNU diff regarding --label
Various options to "diff(1)" show filenames, and traditionally make use of the
"--label" parameter, if set.

Restore this behaviour in BSD diff.

While here add a regression test

PR:		244533
Submitted by:	Jamie Landeg-Jones <jamie@catflap.org>
MFC after:	3 days
2020-06-01 09:01:13 +00:00
..
2018-06-12 16:42:11 +00:00