xzdiff, xzgrep, and xzmore: Rewrite the man pages.

The main reason is a kind of silly one:

xz-man.pot contains strings from all man pages in XZ Utils.
The man pages of xzdiff, xzgrep, and xzmore were under GPLv2
and the rest under 0BSD. Thus xz-man.pot contained strings
under two licences. po4a creates the translated man pages
from the combined 0BSD+GPLv2 xz-man.pot.

I haven't liked this mixing in xz-man.pot but the
Translation Project requires that all man pages must be
in the same .pot file. So a separate xz-man-gpl.pot
wasn't an option.

Since these man pages are short, rewriting them was quick enough.
Now xz-man.pot is entirely under 0BSD and marking the per-file
licenses is simpler.

As a bonus, some wording hopefully is now slightly better
although it's perhaps a matter of taste.

NOTE: In xzgrep.1, the EXIT STATUS section was written by me
in the commit d796b6d7fdb8b7238b277056cf9146cce25db604 so that's
why that section could be taken as is from the old xzgrep.1.

1 files changed, 73 insertions, 43 deletions

diff --git a/src/scripts/xzgrep.1 b/src/scripts/xzgrep.1
index 0ace8502..d60a0516 100644
--- a/src/scripts/xzgrep.1
+++ b/src/scripts/xzgrep.1
@@ -1,18 +1,18 @@
-.\" SPDX-License-Identifier: GPL-2.0-or-later
+.\" SPDX-License-Identifier: 0BSD
 .\"
-.\" Original zgrep.1 for gzip: Jean-loup Gailly
-.\"                            Charles Levert <charles@comm.polymtl.ca>
+.\" Authors: Lasse Collin
+.\"          Jia Tan
 .\"
-.\" Modifications for XZ Utils: Lasse Collin
+.\" (Note that this file is not based on gzip's zgrep.1.)
 .\"
-.TH XZGREP 1 "2022-07-19" "Tukaani" "XZ Utils"
+.TH XZGREP 1 "2024-02-12" "Tukaani" "XZ Utils"
 .SH NAME
-xzgrep \- search compressed files for a regular expression
+xzgrep \- search possibly-compressed files for patterns
+.
 .SH SYNOPSIS
 .B xzgrep
-.RI [ grep_options ]
-.RB [ \-e ]
-.I pattern
+.RI [ option... ]
+.RI [ pattern_list ]
 .RI [ file... ]
 .br
 .B xzegrep
@@ -29,54 +29,83 @@ xzgrep \- search compressed files for a regular expression
 .br
 .B lzfgrep
 \&...
+.
 .SH DESCRIPTION
 .B xzgrep
 invokes
 .BR grep (1)
-on
+on uncompressed contents of files.
+The formats of the
 .I files
-which may be either uncompressed or compressed with
+are determined from the filename suffixes.
+Any
+.I file
+with a suffix supported by
 .BR xz (1),
-.BR lzma (1),
 .BR gzip (1),
 .BR bzip2 (1),
 .BR lzop (1),
 or
-.BR zstd (1).
-All options specified are passed directly to
-.BR grep (1).
+.BR zstd (1)
+will be decompressed;
+all other files are assumed to be uncompressed.
 .PP
 If no
+.I files
+are specified or
 .I file
-is specified, then standard input is decompressed if necessary
-and fed to
-.BR grep (1).
-When reading from standard input,
-.BR gzip (1),
-.BR bzip2 (1),
-.BR lzop (1),
-and
-.BR zstd (1)
-compressed files are not supported.
+is
+.B \-
+then standard input is read.
+When reading from standard input, only files supported by
+.BR xz (1)
+are decompressed.
+Other files are assumed to be in uncompressed form already.
+.PP
+Most
+.I options
+of
+.BR grep (1)
+are supported.
+However, the following options are not supported:
+.IP "" 4
+.BR \-r ,
+.B \-\-recursive
+.IP "" 4
+.BR \-R ,
+.B \-\-dereference\-recursive
+.IP "" 4
+.BR \-d ,
+.BI \-\-directories= action
+.IP "" 4
+.BR \-Z ,
+.B \-\-null
+.IP "" 4
+.BR \-z ,
+.B \-\-null\-data
+.IP "" 4
+.BI \-\-include= glob
+.IP "" 4
+.BI \-\-exclude= glob
+.IP "" 4
+.BI \-\-exclude\-from= file
+.IP "" 4
+.BI \-\-exclude\-dir= glob
 .PP
-If
-.B xzgrep
-is invoked as
 .B xzegrep
-or
+is an alias for
+.BR "xzgrep \-E" .
 .B xzfgrep
-then
-.B grep \-E
-or
-.B grep \-F
-is used instead of
-.BR grep (1).
-The same applies to names
+is an alias for
+.BR "xzgrep \-F" .
+.PP
+The commands
 .BR lzgrep ,
 .BR lzegrep ,
 and
-.BR lzfgrep ,
-which are provided for backward compatibility with LZMA Utils.
+.B lzfgrep
+are provided for backward compatibility with LZMA Utils.
+.
 .SH EXIT STATUS
 .TP
 0
@@ -90,18 +119,19 @@ No errors occurred.
 >1
 One or more errors occurred.
 It is unknown if matches were found.
+.
 .SH ENVIRONMENT
 .TP
 .B GREP
-If the
+If
 .B GREP
-environment variable is set,
-.B xzgrep
-uses it instead of
-.BR grep (1),
+is set to a non-empty value,
+it is used instead of
+.BR "grep" ,
 .BR "grep \-E" ,
 or
 .BR "grep \-F" .
+.
 .SH "SEE ALSO"
 .BR grep (1),
 .BR xz (1),