nixpkgs/nixos/doc/manual/release-notes/rl-unstable.xml

<section xmlns="http://docbook.org/ns/docbook"
         xmlns:xlink="http://www.w3.org/1999/xlink"
         xmlns:xi="http://www.w3.org/2001/XInclude"
         version="5.0"
         xml:id="sec-release-unstable">

<title>Unstable</title>

<para>When upgrading from a previous release, please be aware of the
following incompatible changes:</para>

<itemizedlist>
  <listitem>
    <para><command>wmiiSnap</command> has been replaced with
    <command>wmii_hg</command>, but
    <command>services.xserver.windowManager.wmii.enable</command> has
    been updated respectively so this only affects you if you have
    explicitly installed <command>wmiiSnap</command>.
    </para>
  </listitem>

  <listitem>
    <para><command>wmiimenu</command> is removed, as it has been
    removed by the developers upstream. Use <command>wimenu</command>
    from the <command>wmii-hg</command> package.</para>
  </listitem>

  <listitem>
    <para>Gitit is no longer automatically added to the module list in
    NixOS and as such there will not be any manual entries for it. You
    will need to add an import statement to your NixOS configuration
    in order to use it, e.g.

<programlisting><![CDATA[
{
  imports = [ <nixos/modules/services/misc/gitit.nix> ];
}
]]></programlisting>

    will include the Gitit service configuration options.</para>
  </listitem>

  <listitem>
    <para><command>nginx</command> does not accept flags for enabling and
    disabling modules anymore. Instead it accepts <literal>modules</literal>
    argument, which is a list of modules to be built in. All modules now
    reside in <literal>nginxModules</literal> set. Example configuration:

<programlisting><![CDATA[
nginx.override {
  modules = [ nginxModules.rtmp nginxModules.dav nginxModules.moreheaders ];
}
]]></programlisting>
    </para>
  </listitem>

</itemizedlist>

</section>