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<chapter id='dev-manual-newbie'>

<title>The Yocto Project Open Source Development Environment</title>

<section id="usingpoky-changes-collaborate">
    <title>Using the Yocto Project in a Team Environment</title>

    <para>
        It might not be immediately clear how you can use the Yocto
        Project in a team environment, or scale it for a large team of
        developers.
        One of the strengths of the Yocto Project is that it is extremely
        flexible.
        Thus, you can adapt it to many different use cases and scenarios.
        However, these characteristics can cause a struggle if you are trying
        to create a working setup that scales across a large team.
    </para>

    <para>
        To help with these types of situations, this section presents
        some of the project's most successful experiences,
        practices, solutions, and available technologies that work well.
        Keep in mind, the information here is a starting point.
        You can build off it and customize it to fit any
        particular working environment and set of practices.
    </para>

    <section id='best-practices-system-configurations'>
        <title>System Configurations</title>

        <para>
            Systems across a large team should meet the needs of
            two types of developers: those working on the contents of the
            operating system image itself and those developing applications.
            Regardless of the type of developer, their workstations must
            be both reasonably powerful and run Linux.
        </para>

        <section id='best-practices-application-development'>
            <title>Application Development</title>

            <para>
                For developers who mainly do application level work
                on top of an existing software stack,
                the following list shows practices that work best.
                For information on using a Software Development Kit (SDK), see
                the
                <ulink url='&YOCTO_DOCS_SDK_URL;#sdk-intro'>Yocto Project Software Development Kit (SDK) Developer's Guide</ulink>:
                <itemizedlist>
                    <listitem><para>Use a pre-built toolchain that
                        contains the software stack itself.
                        Then, develop the application code on top of the
                        stack.
                        This method works well for small numbers of relatively
                        isolated applications.</para></listitem>
                    <listitem><para>When possible, use the Yocto Project
                        plug-in for the <trademark class='trade'>Eclipse</trademark> IDE
                        and SDK development practices.
                        For more information, see the
                        "<ulink url='&YOCTO_DOCS_SDK_URL;'>Yocto Project Software Development Kit (SDK) Developer's Guide</ulink>".
                        </para></listitem>
                    <listitem><para>Keep your cross-development toolchains
                        updated.
                        You can do this through provisioning either as new
                        toolchain downloads or as updates through a package
                        update mechanism using <filename>opkg</filename>
                        to provide updates to an existing toolchain.
                        The exact mechanics of how and when to do this are a
                        question for local policy.</para></listitem>
                    <listitem><para>Use multiple toolchains installed locally
                        into different locations to allow development across
                        versions.</para></listitem>
                </itemizedlist>
            </para>
        </section>

        <section id='best-practices-core-system-development'>
            <title>Core System Development</title>

            <para>
                For core system development, it is often best to have the
                build system itself available on the developer workstations
                so developers can run their own builds and directly
                rebuild the software stack.
                You should keep the core system unchanged as much as
                possible and do your work in layers on top of the core system.
                Doing so gives you a greater level of portability when
                upgrading to new versions of the core system or Board
                Support Packages (BSPs).
                You can share layers amongst the developers of a particular
                project and contain the policy configuration that defines
                the project.
            </para>

            <para>
                Aside from the previous best practices, there exists a number
                of tips and tricks that can help speed up core development
                projects:
                <itemizedlist>
                    <listitem><para>Use a
                        <ulink url='&YOCTO_DOCS_REF_URL;#shared-state-cache'>Shared State Cache</ulink>
                        (sstate) among groups of developers who are on a
                        fast network.
                        The best way to share sstate is through a
                        Network File System (NFS) share.
                        The first user to build a given component for the
                        first time contributes that object to the sstate,
                        while subsequent builds from other developers then
                        reuse the object rather than rebuild it themselves.
                        </para>
                        <para>Although it is possible to use other protocols for the
                        sstate such as HTTP and FTP, you should avoid these.
                        Using HTTP limits the sstate to read-only and
                        FTP provides poor performance.
                        </para></listitem>
                    <listitem><para>Have autobuilders contribute to the sstate
                        pool similarly to how the developer workstations
                        contribute.
                        For information, see the
                        "<link linkend='best-practices-autobuilders'>Autobuilders</link>"
                        section.</para></listitem>
                    <listitem><para>Build stand-alone tarballs that contain
                        "missing" system requirements if for some reason
                        developer workstations do not meet minimum system
                        requirements such as latest Python versions,
                        <filename>chrpath</filename>, or other tools.
                        You can install and relocate the tarball exactly as you
                        would the usual cross-development toolchain so that
                        all developers can meet minimum version requirements
                        on most distributions.</para></listitem>
                    <listitem><para>Use a small number of shared,
                        high performance systems for testing purposes
                        (e.g. dual, six-core Xeons with 24 Gbytes of RAM
                        and plenty of disk space).
                        Developers can use these systems for wider, more
                        extensive testing while they continue to develop
                        locally using their primary development system.
                        </para></listitem>
                    <listitem><para>Enable the PR Service when package feeds
                        need to be incremental with continually increasing
                        <ulink url='&YOCTO_DOCS_REF_URL;#var-PR'>PR</ulink>
                        values.
                        Typically, this situation occurs when you use or
                        publish package feeds and use a shared state.
                        You should enable the PR Service for all users who
                        use the shared state pool.
                        For more information on the PR Service, see the
                        "<link linkend='working-with-a-pr-service'>Working With a PR Service</link>".
                        </para></listitem>
                </itemizedlist>
            </para>
        </section>
    </section>

    <section id='best-practices-source-control-management'>
        <title>Source Control Management (SCM)</title>

        <para>
            Keeping your
            <ulink url='&YOCTO_DOCS_REF_URL;#metadata'>Metadata</ulink>
            and any software you are developing under the
            control of an SCM system that is compatible
            with the OpenEmbedded build system is advisable.
            Of the SCMs BitBake supports, the
            Yocto Project team strongly recommends using
            <ulink url='&YOCTO_DOCS_REF_URL;#git'>Git</ulink>.
            Git is a distributed system that is easy to backup,
            allows you to work remotely, and then connects back to the
            infrastructure.
            <note>
                For information about BitBake, see the
                <ulink url='&YOCTO_DOCS_BB_URL;'>BitBake User Manual</ulink>.
            </note>
        </para>

        <para>
            It is relatively easy to set up Git services and create
            infrastructure like
            <ulink url='&YOCTO_GIT_URL;'>http://git.yoctoproject.org</ulink>,
            which is based on server software called
            <filename>gitolite</filename> with <filename>cgit</filename>
            being used to generate the web interface that lets you view the
            repositories.
            The <filename>gitolite</filename> software identifies users
            using SSH keys and allows branch-based
            access controls to repositories that you can control as little
            or as much as necessary.
        </para>

        <note>
            The setup of these services is beyond the scope of this manual.
            However, sites such as these exist that describe how to perform
            setup:
            <itemizedlist>
                <listitem><para><ulink url='http://git-scm.com/book/ch4-8.html'>Git documentation</ulink>:
                    Describes how to install <filename>gitolite</filename>
                    on the server.</para></listitem>
                <listitem><para><ulink url='http://sitaramc.github.com/gitolite/master-toc.html'>The <filename>gitolite</filename> master index</ulink>:
                    All topics for <filename>gitolite</filename>.
                    </para></listitem>
                <listitem><para><ulink url='https://git.wiki.kernel.org/index.php/Interfaces,_frontends,_and_tools'>Interfaces, frontends, and tools</ulink>:
                    Documentation on how to create interfaces and frontends
                    for Git.</para></listitem>
            </itemizedlist>
        </note>
    </section>

    <section id='best-practices-autobuilders'>
        <title>Autobuilders</title>

        <para>
            Autobuilders are often the core of a development project.
            It is here that changes from individual developers are brought
            together and centrally tested and subsequent decisions about
            releases can be made.
            Autobuilders also allow for "continuous integration" style
            testing of software components and regression identification
            and tracking.
        </para>

        <para>
            See "<ulink url='http://autobuilder.yoctoproject.org'>Yocto Project Autobuilder</ulink>"
            for more information and links to buildbot.
            The Yocto Project team has found this implementation
            works well in this role.
            A public example of this is the Yocto Project
            Autobuilders, which we use to test the overall health of the
            project.
        </para>

        <para>
            The features of this system are:
            <itemizedlist>
                <listitem><para>Highlights when commits break the build.
                    </para></listitem>
                <listitem><para>Populates an sstate cache from which
                    developers can pull rather than requiring local
                    builds.</para></listitem>
                <listitem><para>Allows commit hook triggers,
                    which trigger builds when commits are made.
                    </para></listitem>
                <listitem><para>Allows triggering of automated image booting
                    and testing under the QuickEMUlator (QEMU).
                    </para></listitem>
                <listitem><para>Supports incremental build testing and
                    from-scratch builds.</para></listitem>
                <listitem><para>Shares output that allows developer
                    testing and historical regression investigation.
                    </para></listitem>
                <listitem><para>Creates output that can be used for releases.
                    </para></listitem>
                <listitem><para>Allows scheduling of builds so that resources
                    can be used efficiently.</para></listitem>
            </itemizedlist>
        </para>
    </section>

    <section id='best-practices-policies-and-change-flow'>
        <title>Policies and Change Flow</title>

        <para>
            The Yocto Project itself uses a hierarchical structure and a
            pull model.
            Scripts exist to create and send pull requests
            (i.e. <filename>create-pull-request</filename> and
            <filename>send-pull-request</filename>).
            This model is in line with other open source projects where
            maintainers are responsible for specific areas of the project
            and a single maintainer handles the final "top-of-tree" merges.
        </para>

        <note>
            You can also use a more collective push model.
            The <filename>gitolite</filename> software supports both the
            push and pull models quite easily.
        </note>

        <para>
            As with any development environment, it is important
            to document the policy used as well as any main project
            guidelines so they are understood by everyone.
            It is also a good idea to have well structured
            commit messages, which are usually a part of a project's
            guidelines.
            Good commit messages are essential when looking back in time and
            trying to understand why changes were made.
        </para>

        <para>
            If you discover that changes are needed to the core layer of the
            project, it is worth sharing those with the community as soon
            as possible.
            Chances are if you have discovered the need for changes, someone
            else in the community needs them also.
        </para>
    </section>

    <section id='best-practices-summary'>
        <title>Summary</title>

        <para>
            This section summarizes the key recommendations described in the
            previous sections:
            <itemizedlist>
                <listitem><para>Use <ulink url='&YOCTO_DOCS_REF_URL;#git'>Git</ulink>
                    as the source control system.</para></listitem>
                <listitem><para>Maintain your Metadata in layers that make sense
                    for your situation.
                    See the "<link linkend='understanding-and-creating-layers'>Understanding
                    and Creating Layers</link>" section for more information on
                    layers.</para></listitem>
                <listitem><para>
                    Separate the project's Metadata and code by using
                    separate Git repositories.
                    See the
                    "<ulink url='&YOCTO_DOCS_REF_URL;#yocto-project-repositories'>Yocto Project Source Repositories</ulink>"
                    section for information on these repositories.
                    See the
                    "<link linkend='getting-setup'>Getting Set Up</link>"
                    section for information on how to set up local Git
                    repositories for related upstream Yocto Project
                    Git repositories.
                    </para></listitem>
                <listitem><para>Set up the directory for the shared state cache
                    (<ulink url='&YOCTO_DOCS_REF_URL;#var-SSTATE_DIR'><filename>SSTATE_DIR</filename></ulink>)
                    where it makes sense.
                    For example, set up the sstate cache on a system used
                    by developers in the same organization and share the
                    same source directories on their machines.
                    </para></listitem>
                <listitem><para>Set up an Autobuilder and have it populate the
                    sstate cache and source directories.</para></listitem>
                <listitem><para>The Yocto Project community encourages you
                    to send patches to the project to fix bugs or add features.
                    If you do submit patches, follow the project commit
                    guidelines for writing good commit messages.
                    See the "<link linkend='how-to-submit-a-change'>How to Submit a Change</link>"
                    section.</para></listitem>
                <listitem><para>Send changes to the core sooner than later
                    as others are likely to run into the same issues.
                    For some guidance on mailing lists to use, see the list in the
                    "<link linkend='how-to-submit-a-change'>How to Submit a Change</link>"
                    section.
                    For a description of the available mailing lists, see the
                    "<ulink url='&YOCTO_DOCS_REF_URL;#resources-mailinglist'>Mailing Lists</ulink>"
                    section in the Yocto Project Reference Manual.
                    </para></listitem>
            </itemizedlist>
        </para>
    </section>
</section>

<section id='submitting-a-defect-against-the-yocto-project'>
    <title>Submitting a Defect Against the Yocto Project</title>

    <para>
        Use the Yocto Project implementation of
        <ulink url='http://www.bugzilla.org/about/'>Bugzilla</ulink>
        to submit a defect (bug) against the Yocto Project.
        For additional information on this implementation of Bugzilla see the
        "<ulink url='&YOCTO_DOCS_REF_URL;#resources-bugtracker'>Yocto Project Bugzilla</ulink>"
        section in the Yocto Project Reference Manual.
        For more detail on any of the following steps, see the Yocto Project
        <ulink url='&YOCTO_WIKI_URL;/wiki/Bugzilla_Configuration_and_Bug_Tracking'>Bugzilla wiki page</ulink>.
    </para>

    <para>
        Use the following general steps to submit a bug"

        <orderedlist>
            <listitem><para>
                Open the Yocto Project implementation of
                <ulink url='&YOCTO_BUGZILLA_URL;'>Bugzilla</ulink>.
                </para></listitem>
            <listitem><para>
                Click "File a Bug" to enter a new bug.
                </para></listitem>
            <listitem><para>
                Choose the appropriate "Classification", "Product", and
                "Component" for which the bug was found.
                Bugs for the Yocto Project fall into one of several
                classifications, which in turn break down into several
                products and components.
                For example, for a bug against the
                <filename>meta-intel</filename> layer, you would choose
                "Build System, Metadata &amp; Runtime", "BSPs", and
                "bsps-meta-intel", respectively.
                </para></listitem>
            <listitem><para>
                Choose the "Version" of the Yocto Project for which you found
                the bug (e.g. &DISTRO;).
                </para></listitem>
            <listitem><para>
                Determine and select the "Severity" of the bug.
                The severity indicates how the bug impacted your work.
                </para></listitem>
            <listitem><para>
                Choose the "Hardware" that the bug impacts.
                </para></listitem>
            <listitem><para>
                Choose the "Architecture" that the bug impacts.
                </para></listitem>
            <listitem><para>
                Choose a "Documentation change" item for the bug.
                Fixing a bug might or might not affect the Yocto Project
                documentation.
                If you are unsure of the impact to the documentation, select
                "Don't Know".
                </para></listitem>
            <listitem><para>
                Provide a brief "Summary" of the bug.
                Try to limit your summary to just a line or two and be sure
                to capture the essence of the bug.
                </para></listitem>
            <listitem><para>
                Provide a detailed "Description" of the bug.
                You should provide as much detail as you can about the context,
                behavior, output, and so forth that surrounds the bug.
                You can even attach supporting files for output from logs by
                using the "Add an attachment" button.
                </para></listitem>
            <listitem><para>
                Click the "Submit Bug" button submit the bug.
                A new Bugzilla number is assigned to the bug and the defect
                is logged in the bug tracking system.
                </para></listitem>
        </orderedlist>
        Once you file a bug, the bug is processed by the Yocto Project Bug
        Triage Team and further details concerning the bug are assigned
        (e.g. priority and owner).
        You are the "Submitter" of the bug and any further categorization,
        progress, or comments on the bug result in Bugzilla sending you an
        automated email concerning the particular change or progress to the
        bug.
    </para>
</section>

<section id='how-to-submit-a-change'>
    <title>How to Submit a Change</title>

    <para>
        Contributions to the Yocto Project and OpenEmbedded are very welcome.
        Because the system is extremely configurable and flexible, we recognize that developers
        will want to extend, configure or optimize it for their specific uses.
        You should send patches to the appropriate mailing list so that they
        can be reviewed and merged by the appropriate maintainer.
    </para>

    <section id='submit-change-overview'>
        <title>Overview</title>

        <para>
            The Yocto Project uses a mailing list and patch-based workflow
            that is similar to the Linux kernel but contains important
            differences.
            In general, a mailing list exists through which you can submit
            patches.
            The specific mailing list you need to use depends on the
            location of the code you are changing.
            Each component (e.g. layer) should have a
            <filename>README</filename> file that indicates where to send
            the changes and which process to follow.
        </para>

        <para>
            You can send the patch to the mailing list using whichever approach
            you feel comfortable with to generate the patch.
            Once sent, the patch is usually reviewed by the community at large.
            If somebody has concerns with the patch, they will usually voice
            their concern over the mailing list.
            If a patch does not receive any negative reviews, the maintainer of
            the affected layer typically takes the patch, tests it, and then
            based on successful testing, merges the patch.
        </para>

        <para>
            Specific to OpenEmbedded-Core, two commonly used testing trees
            exist:
            <itemizedlist>
                <listitem><para>
                    <emphasis>"ross/mut" branch:</emphasis>
                    The "mut" (master-under-test) tree
                    exists in the <filename>poky-contrib</filename> repository
                    in the
                    <ulink url='&YOCTO_GIT_URL;'>Yocto Project source repositories</ulink>.
                    </para></listitem>
                <listitem><para>
                    <emphasis>"master-next" branch:</emphasis>
                    This branch is part of the main
                    "poky" repository in the Yocto Project source repositories.
                    </para></listitem>
            </itemizedlist>
            Maintainers use these branches to test submissions prior to merging
            patches.
            Thus, you can get an idea of the status of a patch based on
            whether the patch has been merged into one of these branches.
        </para>

        <para>
            This system is imperfect and patches can sometimes get lost in the
            flow.
            Asking about the status of a patch is reasonable if the patch
            has been idle for a while with no feedback.
            The Yocto Project does have plans to use
            <ulink url='https://en.wikipedia.org/wiki/Patchwork_(software)'>Patchwork</ulink>
            to track the status of patches and also to automatically preview
            patches.
        </para>

        <para>
            The following sections provide general instructions for both
            pushing changes upstream and for submitting changes as patches.
        </para>
    </section>

    <section id='submit-change-submissions-to-poky'>
        <title>Submissions to Poky</title>

        <para>
            The "poky" repository, which is the Yocto Project's reference build
            environment, is a hybrid repository that contains several
            individual pieces (e.g. BitBake, OpenEmbedded-Core, meta-yocto,
            documentation, and so forth) built using the combo-layer tool.
            The upstream location used for submitting changes varies by
            component:
            <itemizedlist>
                <listitem><para>
                    <emphasis>Core Metadata:</emphasis>
                    Send your patch to the
                    <ulink url='http://lists.openembedded.org/mailman/listinfo/openembedded-core'>openembedded-core</ulink>
                    mailing list.  For example, a change to anything under
                    the <filename>meta</filename> or
                    <filename>scripts</filename> directories should be sent
                    to this mailing list.
                    </para></listitem>
                <listitem><para>
                    <emphasis>BitBake:</emphasis>
                    For changes to BitBake (i.e. anything under the
                    <filename>bitbake</filename> directory), send your patch
                    to the
                    <ulink url='http://lists.openembedded.org/mailman/listinfo/bitbake-devel'>bitbake-devel</ulink>
                    mailing list.
                    </para></listitem>
                <listitem><para>
                    <emphasis>"meta-yocto-bsp" and "meta-poky" trees:</emphasis>
                    These trees are
                    part of the "meta-yocto" repository in the Yocto Project
                    source repositories.
                    Use the
                    <ulink url='https://lists.yoctoproject.org/listinfo/poky'>poky</ulink>
                    mailing list.
                    </para></listitem>
            </itemizedlist>
        </para>
    </section>

    <section id='submit-change-submissions-to-other-layers'>
        <title>Submissions to Other Layers</title>

        <para>
            For changes to other layers hosted in the Yocto Project source
            repositories (i.e. <filename>yoctoproject.org</filename>), tools,
            and the Yocto Project documentation, use the
            <ulink url='https://lists.yoctoproject.org/listinfo/yocto'>Yocto Project</ulink>
            general mailing list.
            <note>
                Sometimes a layer's documentation specifies to use a
                particular mailing list.
                If so, use that list.
            </note>
            For additional recipes that do not fit into the core Metadata, you
            should determine which layer the recipe should go into and submit
            the change in the manner recommended by the documentation (e.g.
            the <filename>README</filename> file) supplied with the layer.
            If in doubt, please ask on the Yocto general mailing list or on
            the openembedded-devel mailing list.
        </para>
    </section>

    <section id='submit-change-patch-submission-details'>
        <title>Patch Submission Details</title>

        <para>
            When submitting any change, you can check who you should be
            notifying.
            Use either of these methods to find out:
            <itemizedlist>
                <listitem><para>
                    <emphasis>Maintenance File:</emphasis>
                    Examine the <filename>maintainers.inc</filename> file, which is
                    located in the
                    <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>
                    at <filename>meta-poky/conf/distro/include</filename>, to
                    see who is responsible for code.
                    </para></listitem>
                <listitem><para>
                    <emphasis>Search by File:</emphasis>
                    Using <ulink url='&YOCTO_DOCS_REF_URL;#git'>Git</ulink>, you can enter the
                    following command to bring up a short list of all commits
                    against a specific file:
                    <literallayout class='monospaced'>
     git shortlog -- <replaceable>filename</replaceable>
                    </literallayout>
                    Just provide the name of the file for which you are interested.
                    The information returned is not ordered by history but does
                    include a list of everyone who has committed grouped by
                    name.
                    From the list, you can see who is responsible for the bulk of
                    the changes against the file.
                    </para></listitem>
            </itemizedlist>
        </para>

        <para>
            For a list of the Yocto Project and related mailing lists, see the
            "<ulink url='&YOCTO_DOCS_REF_URL;#resources-mailinglist'>Mailing lists</ulink>"
            section in the Yocto Project Reference Manual.
        </para>

        <para>
            When you send a patch, be sure to include a "Signed-off-by:"
            line in the same style as required by the Linux kernel.
            Adding this line signifies that you, the submitter, have agreed
            to the Developer's Certificate of Origin 1.1 as follows:
            <literallayout class='monospaced'>
     Developer's Certificate of Origin 1.1

     By making a contribution to this project, I certify that:

     (a) The contribution was created in whole or in part by me and I
         have the right to submit it under the open source license
         indicated in the file; or

     (b) The contribution is based upon previous work that, to the best
         of my knowledge, is covered under an appropriate open source
         license and I have the right under that license to submit that
         work with modifications, whether created in whole or in part
         by me, under the same open source license (unless I am
         permitted to submit under a different license), as indicated
         in the file; or

     (c) The contribution was provided directly to me by some other
         person who certified (a), (b) or (c) and I have not modified
         it.

     (d) I understand and agree that this project and the contribution
         are public and that a record of the contribution (including all
         personal information I submit with it, including my sign-off) is
         maintained indefinitely and may be redistributed consistent with
         this project or the open source license(s) involved.
            </literallayout>
        </para>

        <para>
            In a collaborative environment, it is necessary to have some sort
            of standard or method through which you submit changes.
            Otherwise, things could get quite chaotic.
            One general practice to follow is to make small, controlled changes.
            Keeping changes small and isolated aids review, makes
            merging/rebasing easier and keeps the change history clean should
            anyone need to refer to it in future.
        </para>

        <para>
            When you make a commit, you must follow certain standards
            established by the OpenEmbedded and Yocto Project development teams.
            For each commit, you must provide a single-line summary of the
            change and you should almost always provide a more detailed
            description of what you did (i.e. the body of the commit message).
            The only exceptions for not providing a detailed description would
            be if your change is a simple, self-explanatory change that needs
            no further description beyond the summary.
            Here are the guidelines for composing a commit message:
            <itemizedlist>
                <listitem><para>
                    Provide a single-line, short summary of the change.
                    This summary is typically viewable in the "shortlist" of
                    changes.
                    Thus, providing something short and descriptive that
                    gives the reader a summary of the change is useful when
                    viewing a list of many commits.
                    You should prefix this short description with the recipe
                    name (if changing a recipe), or else with the short form
                    path to the file being changed.
                    </para></listitem>
                <listitem><para>
                    For the body of the commit message, provide detailed
                    information that describes what you changed, why you made
                    the change, and the approach you used.
                    It might also be helpful if you mention how you tested
                    the change.
                    Provide as much detail as you can in the body of the
                    commit message.
                    </para></listitem>
                <listitem><para>
                    If the change addresses a specific bug or issue that is
                    associated with a bug-tracking ID, include a reference
                    to that ID in your detailed description.
                    For example, the Yocto Project uses a specific convention
                    for bug references - any commit that addresses a specific
                    bug should use the following form for the detailed
                    description:
                    <literallayout class='monospaced'>
     Fixes [YOCTO #<replaceable>bug-id</replaceable>]

     <replaceable>detailed description of change</replaceable>
                    </literallayout>
                    </para></listitem>
                Where <replaceable>bug-id</replaceable> is replaced with the
                specific bug ID from the Yocto Project Bugzilla instance.
            </itemizedlist>
        </para>

        <para>
            You can find more guidance on creating well-formed commit messages
            at this OpenEmbedded wiki page:
            <ulink url='&OE_HOME_URL;/wiki/Commit_Patch_Message_Guidelines'></ulink>.
        </para>
    </section>

    <section id='pushing-a-change-upstream'>
        <title>Using Scripts to Push a Change Upstream and Request a Pull</title>

        <para>
            The basic flow for pushing a change to an upstream "contrib" Git repository is as follows:
            <itemizedlist>
                <listitem><para>Make your changes in your local Git repository.</para></listitem>
                <listitem><para>Stage your changes by using the <filename>git add</filename>
                    command on each file you changed.</para></listitem>
                <listitem><para>
                    Commit the change by using the
                    <filename>git commit</filename> command.
                    Be sure to provide a commit message that follows the
                    project’s commit message standards as described earlier.
                    </para></listitem>
                <listitem><para>
                    Push the change to the upstream "contrib" repository by
                    using the <filename>git push</filename> command.
                    </para></listitem>
                <listitem><para>Notify the maintainer that you have pushed a change by making a pull
                    request.
                    The Yocto Project provides two scripts that conveniently let you generate and send
                    pull requests to the Yocto Project.
                    These scripts are <filename>create-pull-request</filename> and
                    <filename>send-pull-request</filename>.
                    You can find these scripts in the <filename>scripts</filename> directory
                    within the <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>.</para>
                    <para>Using these scripts correctly formats the requests without introducing any
                    whitespace or HTML formatting.
                    The maintainer that receives your patches needs to be able to save and apply them
                    directly from your emails.
                    Using these scripts is the preferred method for sending patches.</para>
                    <para>For help on using these scripts, simply provide the
                    <filename>-h</filename> argument as follows:
                    <literallayout class='monospaced'>
     $ poky/scripts/create-pull-request -h
     $ poky/scripts/send-pull-request -h
                    </literallayout></para></listitem>
            </itemizedlist>
        </para>

        <para>
            You can find general Git information on how to push a change upstream in the
            <ulink url='http://git-scm.com/book/en/v2/Distributed-Git-Distributed-Workflows'>Git Community Book</ulink>.
        </para>
    </section>

    <section id='submitting-a-patch'>
        <title>Using Email to Submit a Patch</title>

        <para>
            You can submit patches without using the <filename>create-pull-request</filename> and
            <filename>send-pull-request</filename> scripts described in the previous section.
            However, keep in mind, the preferred method is to use the scripts.
        </para>

        <para>
            Depending on the components changed, you need to submit the email
            to a specific mailing list.
            For some guidance on which mailing list to use, see the list in the
            "<link linkend='how-to-submit-a-change'>How to Submit a Change</link>"
            section.
            For a description of the available mailing lists, see the
            "<ulink url='&YOCTO_DOCS_REF_URL;#resources-mailinglist'>Mailing Lists</ulink>"
            section in the Yocto Project Reference Manual.
        </para>

        <para>
            Here is the general procedure on how to submit a patch through email without using the
            scripts:
            <orderedlist>
                <listitem><para>
                    Make your changes in your local Git repository.
                    </para></listitem>
                <listitem><para>
                    Stage your changes by using the
                    <filename>git add</filename> command on each file you
                    changed.
                    </para></listitem>
                <listitem><para>
                    Commit the change by using the
                    <filename>git commit --signoff</filename> command.
                    Using the <filename>--signoff</filename> option identifies
                    you as the person making the change and also satisfies
                    the Developer's Certificate of Origin (DCO) shown earlier.
                    </para>
                    <para>When you form a commit, you must follow certain
                    standards established by the Yocto Project development
                    team.
                    See the earlier section
                    "<link linkend='how-to-submit-a-change'>How to Submit a Change</link>"
                    for Yocto Project commit message standards.
                    </para></listitem>
                <listitem><para>Format the commit into an email message.
                    To format commits, use the
                    <filename>git format-patch</filename> command.
                    When you provide the command, you must include a revision
                    list or a number of patches as part of the command.
                    For example, either of these two commands takes your most
                    recent single commit and formats it as an email message in
                    the current directory:
                    <literallayout class='monospaced'>
     $ git format-patch -1
                    </literallayout>
                    or
                    <literallayout class='monospaced'>
     $ git format-patch HEAD~
                    </literallayout></para>
                    <para>After the command is run, the current directory
                    contains a numbered <filename>.patch</filename> file for
                    the commit.</para>
                    <para>If you provide several commits as part of the
                    command, the <filename>git format-patch</filename> command
                    produces a series of numbered files in the current
                    directory – one for each commit.
                    If you have more than one patch, you should also use the
                    <filename>--cover</filename> option with the command,
                    which generates a cover letter as the first "patch" in
                    the series.
                    You can then edit the cover letter to provide a
                    description for the series of patches.
                    For information on the
                    <filename>git format-patch</filename> command,
                    see <filename>GIT_FORMAT_PATCH(1)</filename> displayed
                    using the <filename>man git-format-patch</filename>
                    command.
                    <note>
                        If you are or will be a frequent contributor to the
                        Yocto Project or to OpenEmbedded, you might consider
                        requesting a contrib area and the necessary associated
                        rights.
                    </note>
                    </para></listitem>
                <listitem><para>
                    Import the files into your mail client by using the
                    <filename>git send-email</filename> command.
                    <note>
                        In order to use <filename>git send-email</filename>,
                        you must have the proper Git packages installed on
                        your host.
                        For Ubuntu, Debian, and Fedora the package is
                        <filename>git-email</filename>.
                    </note></para>
                    <para>The <filename>git send-email</filename> command
                    sends email by using a local or remote Mail Transport Agent
                    (MTA) such as <filename>msmtp</filename>,
                    <filename>sendmail</filename>, or through a direct
                    <filename>smtp</filename> configuration in your Git
                    <filename>~/.gitconfig</filename> file.
                    If you are submitting patches through email only, it is
                    very important that you submit them without any whitespace
                    or HTML formatting that either you or your mailer
                    introduces.
                    The maintainer that receives your patches needs to be able
                    to save and apply them directly from your emails.
                    A good way to verify that what you are sending will be
                    applicable by the maintainer is to do a dry run and send
                    them to yourself and then save and apply them as the
                    maintainer would.</para>
                    <para>The <filename>git send-email</filename> command is
                    the preferred method for sending your patches since there
                    is no risk of compromising whitespace in the body of the
                    message, which can occur when you use your own mail client.
                    The command also has several options that let you
                    specify recipients and perform further editing of the
                    email message.
                    For information on how to use the
                    <filename>git send-email</filename> command,
                    see <filename>GIT-SEND-EMAIL(1)</filename> displayed using
                    the <filename>man git-send-email</filename> command.
                    </para></listitem>
            </orderedlist>
        </para>
    </section>
</section>
</chapter>
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