Fw: PATCH: dpkg: Check for gzip --rsyncable

[Jeroen Roovers <jer@gentoo.org>]

Begin forwarded message:

Date: Sun, 6 Nov 2016 12:14:04 +0100
From: Jeroen Roovers <jer@gentoo.org>
To: guillem@debian.org
Subject: PATCH: dpkg: Check for gzip --rsyncable


     Hello Guillem,


dpkg 1.18.11 includes a check for a Debian like environment in order to
decide whether to pass --rsyncable to gzip. However, since gzip 1.7
this option is included. This invalidates the entire comment in
scripts/Dpkg/Compression.pm. Instead, we should infer --rsyncable
support from gzip's usage output at run time. Patch attached.


Kind regards,
     jer

--- a/scripts/Dpkg/Compression.pm
+++ b/scripts/Dpkg/Compression.pm
@@ -81,20 +81,12 @@
 };
 
 #
-# XXX: The gzip package in Debian at some point acquired a Debian-specific
-# --rsyncable option via a vendor patch. Which is not present in most of the
-# major distributions, dpkg downstream systems, nor gzip upstream, who have
-# stated they will most probably not accept it because people should be using
-# pigz instead.
+# If gzip supports --rsyncable (version >=1.7 or the Debian patched variant),
+# we use it. Sadly a non-compliant gzip will not complain about the argument
+# when it does not understand it, so we can only print out the usage and infer
+# --rsyncable support from that.
 #
-# This option should have never been accepted in dpkg, ever. But removing it
-# now would probably cause demands for tarring and feathering. In addition
-# we cannot use the Dpkg::Vendor logic because that would cause circular
-# module dependencies. The whole affair is pretty disgusting really.
-#
-# Check the perl Config to discern Debian and hopefully derivatives too.
-#
-if ($Config{cf_by} eq 'Debian Project') {
+if (system("gzip --help 2>&1 | grep -q -- --rsyncable") == 0) {
     push @{$COMP->{gzip}->{comp_prog}}, '--rsyncable';
 }