doc: Add preliminary section about `release.nix'.
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Ludovic Courtès
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@ -150,15 +150,205 @@ DBIx::Class::ResultSet::create(): DBI Exception: DBD::SQLite::st execute failed:
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</section>
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<section>
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<title><filename>release.nix</filename></title>
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<title>Build Recipes</title>
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- Voorbeelden van Nix expressies voor Hydra:
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<para>
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Build jobs and <emphasis>build recipes</emphasis> for a jobset are
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specified in a text file written in the <link
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xlink:href="http://nixos.org/nix/">Nix language</link>. The
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recipe is actually called a <emphasis>Nix expression</emphasis> in
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Nix parlance. By convention this file is often called
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<filename>release.nix</filename>.
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</para>
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<para>
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The <filename>release.nix</filename> file is typically kept under
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version control, and the repository that contains it one of the
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build inputs of the corresponding–often called
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<literal>hydraConfig</literal> by convention. The repository for
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that file and the actual file name are specified on the web
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interface of Hydra under the <literal>Setup</literal> tab of the
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jobset's overview page, under the <literal>Nix
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expression</literal> heading. See, for example, the <link
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xlink:href="http://hydra.nixos.org/jobset/patchelf/trunk">jobset
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overview page</link> of the PatchELF project, and <link
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xlink:href="https://svn.nixos.org/repos/nix/patchelf/trunk/release.nix">
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the corresponding Nix file</link>.
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</para>
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<para>
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Knowledge of the Nix language is recommended, but the example
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below should already give a good idea of how it works:
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</para>
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https://svn.nixos.org/repos/nix/patchelf/trunk/release.nix
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https://svn.nixos.org/repos/nix/nix/trunk/release.nix
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https://svn.nixos.org/repos/nix/hydra/trunk/release.nix
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<example xml:id='ex-hello'>
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<title><filename>release.nix</filename> file for GNU Hello</title>
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<programlisting>
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{ nixpkgs }: <co xml:id='ex-hello-co-nixpkgs' />
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let
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pkgs = import nixpkgs {}; <co xml:id='ex-hello-co-import-nixpkgs' />
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jobs = rec { <co xml:id='ex-hello-co-jobs' />
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tarball = <co xml:id='ex-hello-co-tarball' />
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{ helloSrc }: <co xml:id='ex-hello-co-tarball-arg' />
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pkgs.releaseTools.sourceTarball { <co xml:id='ex-hello-co-source-tarball' />
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name = "hello-tarball";
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src = helloSrc;
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buildInputs = (with pkgs; [ gettext texLive texinfo ]);
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};
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build = <co xml:id='ex-hello-co-build' />
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{ tarball ? jobs.tarball {} <co xml:id='ex-hello-co-build-args' />
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, system ? builtins.currentSystem
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}:
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let pkgs = import nixpkgs { inherit system; }; in
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pkgs.releaseTools.nixBuild { <co xml:id='ex-hello-co-nix-build' />
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name = "hello" ;
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src = tarball;
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};
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};
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in
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jobs <co xml:id='ex-hello-body' />
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</programlisting>
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</example>
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<para>
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<xref linkend='ex-hello' /> shows what a
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<filename>release.nix</filename> file for <link
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xlink:href="http://www.gnu.org/software/hello/">GNU Hello</link>
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would you like. GNU Hello is representative of many GNU
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and non-GNU free software projects:
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<itemizedlist>
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<listitem>it uses the GNU Build System, namely GNU Autoconf,
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and GNU Automake; for users, it means it can be installed
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using the <link
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xlink:href="http://www.gnu.org/prep/standards/html_node/Managing-Releases.html">usual
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<literal>./configure && make install</literal>
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procedure</link>;
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</listitem>
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<listitem>it uses Gettext for internationalization;</listitem>
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<listitem>it has a Texinfo manual, which can be rendered as PDF
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with TeX.</listitem>
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</itemizedlist>
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The file defines a jobset consisting of two jobs:
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<literal>tarball</literal>, and <literal>build</literal>. It
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contains the following elements (referenced from the figure by
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numbers):
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<calloutlist>
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<callout arearefs='ex-hello-co-nixpkgs'>
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<para>
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This specifies a function of one named arguments,
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<varname>nixpkgs</varname>. This function and those
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defined below is called by Hydra. Here the
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<varname>nixpkgs</varname> argument is meant to be a
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checkout of the <link
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xlink:href="http://nixos.org/nixpkgs/">Nixpkgs</link>
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software distribution.
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</para>
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<para>
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Hydra inspects the formal argument list of the function
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(here, the <varname>nixpkgs</varname> argument) and passes
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it the corresponding parameter specified as a build input
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on Hydra's web interface. In this case, the web interface
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should show a <varname>nixpkgs</varname> build input,
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which is a checkout of the Nixpkgs source code repository.
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</para>
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</callout>
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<callout arearefs='ex-hello-co-import-nixpkgs'>
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<para>
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This defines a variable <varname>pkgs</varname> holding
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the set of packages provided by Nixpkgs.
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</para>
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</callout>
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<callout arearefs='ex-hello-co-jobs'>
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<para>
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This defines a variable holding the two Hydra
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jobs–an <emphasis>attribute set</emphasis> in Nix.
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</para>
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</callout>
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<callout arearefs='ex-hello-co-tarball'>
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<para>
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This is the definition of the first job, named
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<varname>tarball</varname>. The purpose of this job is to
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produce a usable source code tarball.
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</para>
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</callout>
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<callout arearefs='ex-hello-co-tarball-args'>
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<para>
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The <varname>tarball</varname> takes an additional
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argument called <varname>helloSrc</varname>. Again, this
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argument is passed by Hydra and is meant to be a checkout
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of GNU Hello's source code repository.
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</para>
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</callout>
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<callout arearefs='ex-hello-co-source-tarball'>
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<para>
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The <varname>tarball</varname> job calls the
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<varname>sourceTarball</varname> function, which (roughly)
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runs <command>autoreconf && ./configure &&
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make dist</command> on the checkout. The
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<varname>buildInputs</varname> attribute specifies
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additional software dependencies for the job.
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</para>
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</callout>
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<callout arearefs='ex-hello-co-build'>
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<para>
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This is the definition of the <varname>build</varname>
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job, whose purpose is to build Hello from the tarball
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produced above.
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</para>
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</callout>
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<callout arearefs='ex-hello-co-build-args'>
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<para>
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The <varname>build</varname> function takes two additional
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parameter: <varname>tarball</varname>, which is meant to
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be the result of the <varname>tarball</varname> job, and
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<varname>system</varname>, which should be a string
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defining the Nix system type–e.g.,
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<literal>"x86_64-linux"</literal>.
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</para>
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<para>
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Again, these parameters are passed by Hydra when it calls
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<varname>build</varname>. Thus, they must be defined as
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build inputs in Hydra: <varname>tarball</varname> should
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have type <literal>Build Output</literal>, its value being
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the latest output of the <varname>tarball</varname> job,
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and <varname>system</varname> should be a string.
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</para>
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<para>
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The question mark after <literal>tarball</literal> and
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<literal>system</literal> defines default values for these
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arguments, and is only useful for debugging.
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</para>
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</callout>
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<callout arearefs='ex-hello-co-nix-build'>
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<para>
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The <varname>build</varname> job calls the
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<varname>nixBuild</varname> function, which unpacks the
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tarball, then runs <command>./configure && make
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&& make check && make install</command>.
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</para>
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</callout>
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<callout arearefs='ex-hello-co-body'>
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<para>
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Finally, the set of jobs is returned to Hydra, as a Nix
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attribute set.
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</para>
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</callout>
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</calloutlist>
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</para>
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</section>
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<section>
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