+
+ <listitem><para><option>PDiffs</option> (<option>pdiffs</option>)
+ is a yes/no value which controls if APT should try to use PDiffs
+ to update old indexes instead of downloading the new indexes
+ entirely. The value of this option is ignored if the repository
+ doesn't announce the availability of PDiffs. Defaults to the
+ value of the option with the same name for a specific index file
+ defined in the <option>Acquire::IndexTargets</option> scope,
+ which itself defaults to the value of configuration option
+ <option>Acquire::PDiffs</option> which defaults to
+ <literal>yes</literal>.
+ </para></listitem>
+
+ <listitem><para><option>By-Hash</option> (<option>by-hash</option>)
+ can have the value <literal>yes</literal>, <literal>no</literal>
+ or <literal>force</literal> and controls if APT should try to
+ acquire indexes via a URI constructed from a hashsum of the
+ expected file instead of using the well-known stable filename
+ of the index. Using this can avoid hashsum mismatches, but
+ requires a supporting mirror. A <literal>yes</literal> or
+ <literal>no</literal> value activates/disables the use of this
+ feature if this source indicates support for it, while
+ <literal>force</literal> will enable the feature regardless of
+ what the source indicates. Defaults to the value of the option
+ of the same name for a specific index file defined in the
+ <option>Acquire::IndexTargets</option> scope, which itself
+ defaults to the value of configuration option
+ <option>Acquire::By-Hash</option> which defaults to
+ <literal>yes</literal>.
+ </para></listitem>
+