<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 xml:id="submitting-changes-making-patches">
  <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 | nixos/&lt;module>): (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: 54.0.1 -> 55.0</command>
         </para>
        </listitem>
        <listitem>
         <para>
          <command>nixos/hydra: add bazBaz option</command>
         </para>
        </listitem>
        <listitem>
         <para>
          <command>nixos/nginx: 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 xml:id="submitting-changes-submitting-changes">
  <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 | nixos/&lt;module>):
        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 xml:id="submitting-changes-pull-request-template">
  <title>Pull Request Template</title>

  <para>
   The pull request template helps determine what steps have been made for a
   contribution so far, and will help guide maintainers on the status of a
   change. The motivation section of the PR should include any extra details
   the title does not address and link any existing issues related to the pull
   request.
  </para>

  <para>
   When a PR is created, it will be pre-populated with some checkboxes detailed
   below:
  </para>

  <section xml:id="submitting-changes-tested-with-sandbox">
   <title>Tested using sandboxing</title>

   <para>
    When sandbox builds are enabled, Nix will setup an isolated environment for
    each build process. It is used to remove further hidden dependencies set by
    the build environment to improve reproducibility. This includes access to
    the network during the build outside of <function>fetch*</function>
    functions and files outside the Nix store. Depending on the operating
    system access to other resources are blocked as well (ex. inter process
    communication is isolated on Linux); see
    <link
      xlink:href="https://nixos.org/nix/manual/#description-45">build-use-sandbox</link>
    in Nix manual for details.
   </para>

   <para>
    Sandboxing is not enabled by default in Nix due to a small performance hit
    on each build. In pull requests for
    <link
        xlink:href="https://github.com/NixOS/nixpkgs/">nixpkgs</link>
    people are asked to test builds with sandboxing enabled (see
    <literal>Tested using sandboxing</literal> in the pull request template)
    because
    in<link
        xlink:href="https://nixos.org/hydra/">https://nixos.org/hydra/</link>
    sandboxing is also used.
   </para>

   <para>
    Depending if you use NixOS or other platforms you can use one of the
    following methods to enable sandboxing
    <emphasis role="bold">before</emphasis> building the package:
    <itemizedlist>
     <listitem>
      <para>
       <emphasis role="bold">Globally enable sandboxing on NixOS</emphasis>:
       add the following to <filename>configuration.nix</filename>
<screen>nix.useSandbox = true;</screen>
      </para>
     </listitem>
     <listitem>
      <para>
       <emphasis role="bold">Globally enable sandboxing on non-NixOS
       platforms</emphasis>: add the following to:
       <filename>/etc/nix/nix.conf</filename>
<screen>build-use-sandbox = true</screen>
      </para>
     </listitem>
    </itemizedlist>
   </para>
  </section>

  <section xml:id="submitting-changes-platform-diversity">
   <title>Built on platform(s)</title>

   <para>
    Many Nix packages are designed to run on multiple platforms. As such, it's
    important to let the maintainer know which platforms your changes have been
    tested on. It's not always practical to test a change on all platforms, and
    is not required for a pull request to be merged. Only check the systems you
    tested the build on in this section.
   </para>
  </section>

  <section xml:id="submitting-changes-nixos-tests">
   <title>Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)</title>

   <para>
    Packages with automated tests are much more likely to be merged in a timely
    fashion because it doesn't require as much manual testing by the maintainer
    to verify the functionality of the package. If there are existing tests for
    the package, they should be run to verify your changes do not break the
    tests. Tests only apply to packages with NixOS modules defined and can only
    be run on Linux. For more details on writing and running tests, see the
    <link
        xlink:href="https://nixos.org/nixos/manual/index.html#sec-nixos-tests">section
    in the NixOS manual</link>.
   </para>
  </section>

  <section xml:id="submitting-changes-tested-compilation">
   <title>Tested compilation of all pkgs that depend on this change using <command>nox-review</command></title>

   <para>
    If you are updating a package's version, you can use nox to make sure all
    packages that depend on the updated package still compile correctly. This
    can be done using the nox utility. The <command>nox-review</command>
    utility can look for and build all dependencies either based on uncommited
    changes with the <literal>wip</literal> option or specifying a github pull
    request number.
   </para>

   <para>
    review uncommitted changes:
<screen>nix-shell -p nox --run "nox-review wip"</screen>
   </para>

   <para>
    review changes from pull request number 12345:
<screen>nix-shell -p nox --run "nox-review pr 12345"</screen>
   </para>
  </section>

  <section xml:id="submitting-changes-tested-execution">
   <title>Tested execution of all binary files (usually in <filename>./result/bin/</filename>)</title>

   <para>
    It's important to test any executables generated by a build when you change
    or create a package in nixpkgs. This can be done by looking in
    <filename>./result/bin</filename> and running any files in there, or at a
    minimum, the main executable for the package. For example, if you make a
    change to <package>texlive</package>, you probably would only check the
    binaries associated with the change you made rather than testing all of
    them.
   </para>
  </section>

  <section xml:id="submitting-changes-contribution-standards">
   <title>Meets Nixpkgs contribution standards</title>

   <para>
    The last checkbox is fits
    <link
        xlink:href="https://github.com/NixOS/nixpkgs/blob/master/.github/CONTRIBUTING.md">CONTRIBUTING.md</link>.
    The contributing document has detailed information on standards the Nix
    community has for commit messages, reviews, licensing of contributions you
    make to the project, etc... Everyone should read and understand the
    standards the community has for contributing before submitting a pull
    request.
   </para>
  </section>
 </section>
 <section xml:id="submitting-changes-hotfixing-pull-requests">
  <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 xml:id="submitting-changes-commit-policy">
  <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 xml:id="submitting-changes-master-branch">
   <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 xml:id="submitting-changes-staging-branch">
   <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="https://web.archive.org/web/20160528180406/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 xml:id="submitting-changes-stable-release-branches">
   <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>
