2005-12-28  Robert Millan  <address@hidden>

	* src/buffer.c:  Detect, compress and extract p7zip (with -I).
	* src/tar.c:  Ditto.
	* README:  Document p7zip support.
	* doc/tar.texi:  Ditto.

diff -ur tar.old/README tar/README
--- tar.old/README	2005-05-15 05:59:09.000000000 +0200
+++ tar/README	2005-12-14 11:56:44.051330136 +0100
@@ -84,14 +84,15 @@
 
 Here are a few hints which might help installing `tar' on some systems.
 
-** gzip and bzip2.
+** gzip, bzip2 and p7zip.
 
-GNU tar uses the gzip and bzip2 programs to read and write compressed
+GNU tar uses the gzip, bzip2 and p7zip programs to read and write compressed
 archives.  If you don't have these programs already, you need to
 install them.  Their sources can be found at:
 
 ftp://ftp.gnu.org/gnu/gzip/
 http://sourceware.cygnus.com/bzip2/
+http://p7zip.sf.net/
 
 If you see the following symptoms:
 
diff -ur tar.old/doc/tar.texi tar/doc/tar.texi
--- tar.old/doc/tar.texi	2005-12-11 15:10:53.000000000 +0100
+++ tar/doc/tar.texi	2005-12-14 11:55:12.861193144 +0100
@@ -2831,6 +2831,13 @@
 @itemx --old-archive
 Synonym for @option{--format=v7}.
 
address@hidden p7zip, summary
address@hidden --p7zip
address@hidden -I
+
+This option tells @command{tar} to read or write archives through
address@hidden  @xref{gzip}.
+
 @opindex posix, summary
 @item --posix
 Same as @option{--format=posix}.
@@ -3131,6 +3138,10 @@
 
 @option{--incremental}
 
address@hidden -I
+
address@hidden
+
 @item -K
 
 @option{--starting-file}
@@ -7182,19 +7193,20 @@
 @cindex Storing archives in compressed format
 
 @GNUTAR{} is able to create and read compressed archives.  It supports
address@hidden and @command{bzip2} compression programs.  For backward
address@hidden, @command{bzip2} and @command{p7zip} compression programs.  For backward
 compatibilty, it also supports @command{compress} command, although
 we strongly recommend against using it, since there is a patent
 covering the algorithm it uses and you could be sued for patent
 infringement merely by running @command{compress}!  Besides, it is less
-effective than @command{gzip} and @command{bzip2}.
+effective than @command{gzip}, @command{bzip2} or @command{p7zip}.
 
 Creating a compressed archive is simple: you just specify a
 @dfn{compression option} along with the usual archive creation
 commands.  The compression option is @option{-z} (@option{--gzip}) to
 create a @command{gzip} compressed archive, @option{-j}
-(@option{--bzip2}) to create a @command{bzip2} compressed archive, and
address@hidden (@option{--compress}) to use @command{compress} program.
+(@option{--bzip2}) to create a @command{bzip2} compressed archive,
address@hidden (@option{--compress}) to use @command{compress} program, and
address@hidden (@option{--p7zip}) to create a @command{p7zip} compressed archive.
 For example:
 
 @smallexample
diff -ur tar.old/src/buffer.c tar/src/buffer.c
--- tar.old/src/buffer.c	2005-12-09 11:04:26.000000000 +0100
+++ tar/src/buffer.c	2005-12-14 12:00:08.988175000 +0100
@@ -181,7 +181,8 @@
   ct_none,
   ct_compress,
   ct_gzip,
-  ct_bzip2
+  ct_bzip2,
+  ct_p7zip
 };
 
 struct zip_magic
@@ -198,6 +199,7 @@
   { ct_compress, 2, "\037\235", "compress", "-Z" },
   { ct_gzip,     2, "\037\213", "gzip", "-z"  },
   { ct_bzip2,    3, "BZh",      "bzip2", "-j" },
+  { ct_p7zip,    6, "7z\274\257\047\034",      "p7zip", "-I" },
 };
 
 #define NMAGIC (sizeof(magic)/sizeof(magic[0]))
diff -ur tar.old/src/tar.c tar/src/tar.c
--- tar.old/src/tar.c	2005-12-11 15:12:12.000000000 +0100
+++ tar/src/tar.c	2005-12-14 12:02:32.389374704 +0100
@@ -520,6 +520,8 @@
    N_("create archive with volume name TEXT. At list/extract time, use TEXT as a globbing pattern for volume name"), GRID+8 },
   {"bzip2", 'j', 0, 0,
    N_("filter the archive through bzip2"), GRID+8 },
+  {"p7zip", 'I', 0, 0,
+   N_("filter the archive through p7zip"), GRID+8 },
   {"gzip", 'z', 0, 0,
    N_("filter the archive through gzip"), GRID+8 },
   {"gunzip", 0, 0, OPTION_ALIAS, NULL, GRID+8 },
@@ -1002,9 +1004,7 @@
       break;
 
     case 'I':
-      USAGE_ERROR ((0, 0,
-		    _("Warning: the -I option is not supported;"
-		      " perhaps you meant -j or -T?")));
+      set_use_compress_program_option ("p7zip");
       break;
 
     case 'j':