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.. SPDX-License-Identifier: CC-BY-SA-2.0-UK
Using Quilt in Your Workflow
****************************
`Quilt <https://savannah.nongnu.org/projects/quilt>`__ is a powerful tool
that allows you to capture source code changes without having a clean
source tree. This section outlines the typical workflow you can use to
modify source code, test changes, and then preserve the changes in the
form of a patch all using Quilt.
.. note::
With regard to preserving changes to source files, if you clean a
recipe or have :ref:`ref-classes-rm-work` enabled, the
:ref:`devtool workflow <sdk-manual/extensible:using \`\`devtool\`\` in your sdk workflow>`
as described in the Yocto Project Application Development and the
Extensible Software Development Kit (eSDK) manual is a safer
development flow than the flow that uses Quilt.
Follow these general steps:
#. *Find the Source Code:* Temporary source code used by the
OpenEmbedded build system is kept in the :term:`Build Directory`. See the
":ref:`dev-manual/temporary-source-code:finding temporary source code`" section to
learn how to locate the directory that has the temporary source code for a
particular package.
#. *Change Your Working Directory:* You need to be in the directory that
has the temporary source code. That directory is defined by the
:term:`S` variable.
#. *Create a New Patch:* Before modifying source code, you need to
create a new patch. To create a new patch file, use ``quilt new`` as
below::
$ quilt new my_changes.patch
#. *Notify Quilt and Add Files:* After creating the patch, you need to
notify Quilt about the files you plan to edit. You notify Quilt by
adding the files to the patch you just created::
$ quilt add file1.c file2.c file3.c
#. *Edit the Files:* Make your changes in the source code to the files
you added to the patch.
#. *Test Your Changes:* Once you have modified the source code, the
easiest way to test your changes is by calling the :ref:`ref-tasks-compile`
task as shown in the following example::
$ bitbake -c compile -f package
The ``-f`` or ``--force`` option forces the specified task to
execute. If you find problems with your code, you can just keep
editing and re-testing iteratively until things work as expected.
.. note::
All the modifications you make to the temporary source code disappear
once you run the :ref:`ref-tasks-clean` or :ref:`ref-tasks-cleanall`
tasks using BitBake (i.e. ``bitbake -c clean package`` and
``bitbake -c cleanall package``). Modifications will also disappear if
you use the :ref:`ref-classes-rm-work` feature as described in
the ":ref:`dev-manual/disk-space:conserving disk space during builds`"
section.
#. *Generate the Patch:* Once your changes work as expected, you need to
use Quilt to generate the final patch that contains all your
modifications::
$ quilt refresh
At this point, the
``my_changes.patch`` file has all your edits made to the ``file1.c``,
``file2.c``, and ``file3.c`` files.
You can find the resulting patch file in the ``patches/``
subdirectory of the source (:term:`S`) directory.
#. *Copy the Patch File:* For simplicity, copy the patch file into a
directory named ``files``, which you can create in the same directory
that holds the recipe (``.bb``) file or the append (``.bbappend``)
file. Placing the patch here guarantees that the OpenEmbedded build
system will find the patch. Next, add the patch into the :term:`SRC_URI`
of the recipe. Here is an example::
SRC_URI += "file://my_changes.patch"
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