src/usr.bin/gzip/zdiff, branch main

Remove $FreeBSD$: one-line sh pattern

2023-08-16T17:55:03+00:00

Remove /^\s*#[#!]?\s*\$FreeBSD\$.*$\n/

zdiff: avoid non-conformant features

2022-05-31T00:25:16+00:00

`setvar` is a non-conformant feature that looks slightly neater but is
not portable to other /bin/sh implementations.  Making the script
portable is straightforward, so let's do it.

Tests are added to make sure that I didn't break anything major in the
process.

Reviewed by:	bapt (previous version), jilles
Sponsored by:	Klara, Inc.
Differential Revision:	https://reviews.freebsd.org/D35275

Diff reduction against NetBSD. The most notable change is to zdiff(1) to

2011-05-23T09:02:44+00:00

handle more file formats including bzip2 and xz.

MFC after:	2 weeks

Replace the GNU gzip with a slightly modified NetBSD gzip. The

2007-01-26T10:19:08+00:00

NetBSD version is a feature-to-feature re-implementation of GNU
gzip using the freely-redistributable zlib and this version is
expected to be mostly bug-to-bug compatible with the GNU
implementation.

 - Because this is a piece of mature code and we want to make
   changes so it is added directly rather than importing to
   src/contrib.
 - Connect newly added code to src/usr.bin/ and rescue/rescue
   build.
 - Disconnect the GNU gzip code from build for now, they will
   be eventually removed completely.
 - Provide two new src.conf(5) knobs, WITHOUT_BZIP2_SUPPORT and
   WITHOUT_BZIP2.

Tested by:	kris (full exp-7 pointyhat build)
Approved by:	core (importing a 4-clause BSD licensed file)
Approved by:	re (adding new utility during -HEAD code slush)