src/usr.bin/diff/xmalloc.c, branch releng/14.0

Remove $FreeBSD$: one-line .c pattern

2023-08-16T17:54:42+00:00

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

asprintf returns -1, not an arbitrary value < 0. Also upon error the

2020-01-14T08:18:04+00:00

(very sloppy specification) leaves an undefined value in *ret, so it is
wrong to inspect it, the error condition is enough.

Obtained from:	OpenBSD
MFC after:	3 days

Import diff from OpenBSD and remove GNU diff

2017-03-11T05:01:29+00:00

Some of the modifications from the previous summer of code has been integrated
Modification for compatibility with GNU diff output has been added

Main difference with OpenBSD:
Implement multiple GNU diff options:
* --ignore-file-name-case
* --no-ignore-file-name-case
* --normal
* --tabsize
* --strip-trailing-cr
Make diff -p compatible with GNU diff
Implement diff -l
Make diff -r compatible with GNU diff

Capsicumize diffing 2 regular files
Add a simple test suite

Approved by:	AsiaBSDcon devsummit
Obtained from:	OpenBSD, GSoC
Relnotes:	yes