<chapter xmlns="http://docbook.org/ns/docbook"
         xmlns:xlink="http://www.w3.org/1999/xlink"
         xml:id="chap-submitting-changes">

<title>Submitting changes</title>

<section>
<title>Making patches</title>

<itemizedlist>
<listitem>
<para>Read <link xlink:href="https://nixos.org/nixpkgs/manual/">Manual (How to write packages for Nix)</link>.</para>
</listitem>

<listitem>
<para>Fork the repository on GitHub.</para>
</listitem>

<listitem>
<para>Create a branch for your future fix.

<itemizedlist>
<listitem>
<para>You can make branch from a commit of your local <command>nixos-version</command>. That will help you to avoid additional local compilations. Because you will receive packages from binary cache.

<itemizedlist>
<listitem>
<para>For example: <command>nixos-version</command> returns <command>15.05.git.0998212 (Dingo)</command>. So you can do:</para>
</listitem>
</itemizedlist>

<screen>
$ git checkout 0998212
$ git checkout -b 'fix/pkg-name-update'
</screen>
</para>
</listitem>

<listitem>
<para>Please avoid working directly on the <command>master</command> branch.</para>
</listitem>
</itemizedlist>
</para>
</listitem>

<listitem>
<para>Make commits of logical units.

<itemizedlist>
<listitem>
<para>If you removed pkgs, made some major NixOS changes etc., write about them in <command>nixos/doc/manual/release-notes/rl-unstable.xml</command>.</para>
</listitem>
</itemizedlist>
</para>
</listitem>

<listitem>
<para>Check for unnecessary whitespace with <command>git diff --check</command> before committing.</para>
</listitem>

<listitem>
<para>Format the commit in a following way:</para>
<programlisting>
(pkg-name | service-name): (from -> to | init at version | refactor | etc)
Additional information.
</programlisting>

<itemizedlist>
<listitem>
<para>Examples:

<itemizedlist>
<listitem>
<para>
<command>nginx: init at 2.0.1</command>
</para>
</listitem>

<listitem>
<para>
<command>firefox: 3.0 -> 3.1.1</command>
</para>
</listitem>

<listitem>
<para>
<command>hydra service: add bazBaz option</command>
</para>
</listitem>

<listitem>
<para>
<command>nginx service: refactor config generation</command>
</para>
</listitem>
</itemizedlist>
</para>
</listitem>
</itemizedlist>
</listitem>

<listitem>
<para>Test your changes. If you work with

<itemizedlist>
<listitem>
<para>nixpkgs:

<itemizedlist>
<listitem>
<para>update pkg ->

<itemizedlist>
<listitem>
<para>
<command>nix-env -i pkg-name -f &lt;path to your local nixpkgs folder&gt;</command>
</para>
</listitem>
</itemizedlist>
</para>
</listitem>

<listitem>
<para>add pkg ->

<itemizedlist>
<listitem>
<para>Make sure it's in <command>pkgs/top-level/all-packages.nix</command>
</para>
</listitem>

<listitem>
<para>
<command>nix-env -i pkg-name -f &lt;path to your local nixpkgs folder&gt;</command>
</para>
</listitem>
</itemizedlist>
</para>
</listitem>

<listitem>
<para>
<emphasis>If you don't want to install pkg in you profile</emphasis>.

<itemizedlist>
<listitem>
<para>
<command>nix-build -A pkg-attribute-name &lt;path to your local nixpkgs folder&gt;/default.nix</command> and check results in the folder <command>result</command>. It will appear in the same directory where you did <command>nix-build</command>.</para>
</listitem>
</itemizedlist>
</para>
</listitem>

<listitem>
<para>If you did <command>nix-env -i pkg-name</command> you can do <command>nix-env -e pkg-name</command> to uninstall it from your system.</para>
</listitem>
</itemizedlist>
</para>
</listitem>

<listitem>
<para>NixOS and its modules:

<itemizedlist>
<listitem>
<para>You can add new module to your NixOS configuration file (usually it's <command>/etc/nixos/configuration.nix</command>).
            And do <command>sudo nixos-rebuild test -I nixpkgs=&lt;path to your local nixpkgs folder&gt; --fast</command>.</para>
</listitem>
</itemizedlist>
</para>
</listitem>
</itemizedlist>
</para>
</listitem>

<listitem>
<para>If you have commits <command>pkg-name: oh, forgot to insert whitespace</command>: squash commits in this case. Use <command>git rebase -i</command>.</para>
</listitem>

<listitem>
<para>Rebase you branch against current <command>master</command>.</para>
</listitem>
</itemizedlist>
</section>

<section>
<title>Submitting changes</title>

<itemizedlist>
<listitem>
<para>Push your changes to your fork of nixpkgs.</para>
</listitem>

<listitem>
<para>Create pull request:

<itemizedlist>
<listitem>
<para>Write the title in format <command>(pkg-name | service): improvement</command>.

<itemizedlist>
<listitem>
<para>If you update the pkg, write versions <command>from -> to</command>.</para>
</listitem>
</itemizedlist>
</para>
</listitem>

<listitem>
<para>Write in comment if you have tested your patch. Do not rely much on <command>TravisCI</command>.</para>
</listitem>

<listitem>
<para>If you make an improvement, write about your motivation.</para>
</listitem>

<listitem>
<para>Notify maintainers of the package. For example add to the message: <command>cc @jagajaga @domenkozar</command>.</para>
</listitem>
</itemizedlist>
</para>
</listitem>
</itemizedlist>
</section>

<section>
<title>Hotfixing pull requests</title>

<itemizedlist>
<listitem>
<para>Make the appropriate changes in you branch.</para>
</listitem>

<listitem>
<para>Don't create additional commits, do

<itemizedlist>
<listitem>
<para><command>git rebase -i</command></para>
</listitem>
<listitem>
<para>
<command>git push --force</command> to your branch.</para>
</listitem>
</itemizedlist>
</para>
</listitem>

</itemizedlist>
</section>

<section>
<title>Commit policy</title>

<itemizedlist>
<listitem>
<para>Commits must be sufficiently tested before being merged, both for the master and staging branches.</para>
</listitem>

<listitem>
<para>Hydra builds for master and staging should not be used as testing platform, it's a build farm for changes that have been already tested.</para>
</listitem>

<listitem>
<para>When changing the bootloader installation process, extra care must be taken. Grub installations cannot be rolled back, hence changes may break people's installations forever. For any non-trivial change to the bootloader please file a PR asking for review, especially from @edolstra.</para>
</listitem>
</itemizedlist>

<section>
  <title>Master branch</title>

  <itemizedlist>
    <listitem>
      <para>
        It should only see non-breaking commits that do not cause mass rebuilds.
      </para>
    </listitem>
  </itemizedlist>
</section>

<section>
  <title>Staging branch</title>

  <itemizedlist>
    <listitem>
      <para>
        It's only for non-breaking mass-rebuild commits. That means it's not to
        be used for testing, and changes must have been well tested already.
        <link xlink:href="http://comments.gmane.org/gmane.linux.distributions.nixos/13447">Read policy here</link>.
      </para>
    </listitem>
    <listitem>
      <para>
        If the branch is already in a broken state, please refrain from adding
        extra new breakages. Stabilize it for a few days, merge into master,
        then resume development on staging.
        <link xlink:href="http://hydra.nixos.org/jobset/nixpkgs/staging#tabs-evaluations">Keep an eye on the staging evaluations here</link>.
        If any fixes for staging happen to be already in master, then master can
        be merged into staging.
      </para>
    </listitem>
  </itemizedlist>
</section>

<section>
  <title>Stable release branches</title>

  <itemizedlist>
    <listitem>
      <para>
        If you're cherry-picking a commit to a stable release branch, always use
        <command>git cherry-pick -xe</command> and ensure the message contains a
        clear description about why this needs to be included in the stable
        branch.
      </para>
      <para>An example of a cherry-picked commit would look like this:</para>
      <screen>
nixos: Refactor the world.

The original commit message describing the reason why the world was torn apart.

(cherry picked from commit abcdef)
Reason: I just had a gut feeling that this would also be wanted by people from
the stone age.
      </screen>
    </listitem>
  </itemizedlist>
</section>

</section>
</chapter>

