Add a Acquire::CompressionTypes config variable from there the

acquire-items choose which compression file they should (try first to)
download to easily add new or change the order of the compression types.
And because it is easy now we directly add builtin lzma support.

The compression ratio is better than bzip2 but we prefer the later for now
as no (official) mirror uses lzma, so this would only generate useless
hits on the servers. Maybe sometime in the future lzma will be the default...

[apt-pkg/acquire-item.cc]
- use configsettings for dynamic compression type use and order.
  Based on a patch by Jyrki Muukkonen, thanks! (LP: #71746)
[apt-pkg/init.cc]
- add default configuration for compression types and add lzma
  support. Order is now bzip2, lzma, gzip, none (Closes: #510526)
[ftparchive/writer.cc]
- add lzma support also here, patch for this (and inspiration for
  the one above) by Robert Millan, thanks!

1 files changed, 15 insertions, 0 deletions

diff --git a/doc/apt.conf.5.xml b/doc/apt.conf.5.xml
index 85a7d961c..d347bda67 100644
--- a/doc/apt.conf.5.xml
+++ b/doc/apt.conf.5.xml
@@ -303,6 +303,20 @@ DPkg::Pre-Install-Pkgs {"/usr/sbin/dpkg-preconfigure --apt";};
      </para></listitem>
      </varlistentry>
 
+     <varlistentry><term>CompressionTypes</term>
+     <listitem><para>List of compression types which are understood by the acquire methods.
+     Files like <filename>Packages</filename> can be available in various compression formats.
+     This list defines in which order the acquire methods will try to download these files.
+     Per default <command>bzip2</command> compressed files will be prefered over
+     <command>lzma</command>, <command>gzip</command> and uncompressed files. The syntax for
+     the configuration fileentry (this option can't be set at runtime with the -o option) is
+     <synopsis>Acquire::CompressionTypes::<replaceable>FileExtension</replaceable> "<replaceable>Methodname</replaceable>";</synopsis>
+     e.g. <synopsis>Acquire::CompressionTypes::bz2 "bzip2";</synopsis>
+     Note that at runtime the <literal>Dir::Bin::<replaceable>Methodname</replaceable></literal> will
+     be checked: If this setting exists the method will only be used if this file exists, e.g. for
+     the bzip2 method above (the inbuilt) setting is <literallayout>Dir::Bin::bzip2 "/bin/bzip2";</literallayout>
+     </para></listitem>
+     </varlistentry>
    </variablelist>
   </para>
  </refsect1>
@@ -337,6 +351,7 @@ DPkg::Pre-Install-Pkgs {"/usr/sbin/dpkg-preconfigure --apt";};
 
    <para>Binary programs are pointed to by <literal>Dir::Bin</literal>. <literal>Dir::Bin::Methods</literal> 
    specifies the location of the method handlers and <literal>gzip</literal>, 
+   <literal>bzip2</literal>, <literal>lzma</literal>,
    <literal>dpkg</literal>, <literal>apt-get</literal> <literal>dpkg-source</literal> 
    <literal>dpkg-buildpackage</literal> and <literal>apt-cache</literal> specify the location
    of the respective programs.</para>