1.. SPDX-License-Identifier: CC-BY-SA-2.0-UK
2
3Using Quilt in Your Workflow
4****************************
5
6`Quilt <https://savannah.nongnu.org/projects/quilt>`__ is a powerful tool
7that allows you to capture source code changes without having a clean
8source tree. This section outlines the typical workflow you can use to
9modify source code, test changes, and then preserve the changes in the
10form of a patch all using Quilt.
11
12.. note::
13
14   With regard to preserving changes to source files, if you clean a
15   recipe or have :ref:`ref-classes-rm-work` enabled, the
16   :ref:`devtool workflow <sdk-manual/extensible:using \`\`devtool\`\` in your sdk workflow>`
17   as described in the Yocto Project Application Development and the
18   Extensible Software Development Kit (eSDK) manual is a safer
19   development flow than the flow that uses Quilt.
20
21Follow these general steps:
22
23#. *Find the Source Code:* Temporary source code used by the
24   OpenEmbedded build system is kept in the :term:`Build Directory`. See the
25   ":ref:`dev-manual/temporary-source-code:finding temporary source code`" section to
26   learn how to locate the directory that has the temporary source code for a
27   particular package.
28
29#. *Change Your Working Directory:* You need to be in the directory that
30   has the temporary source code. That directory is defined by the
31   :term:`S` variable.
32
33#. *Create a New Patch:* Before modifying source code, you need to
34   create a new patch. To create a new patch file, use ``quilt new`` as
35   below::
36
37      $ quilt new my_changes.patch
38
39#. *Notify Quilt and Add Files:* After creating the patch, you need to
40   notify Quilt about the files you plan to edit. You notify Quilt by
41   adding the files to the patch you just created::
42
43      $ quilt add file1.c file2.c file3.c
44
45#. *Edit the Files:* Make your changes in the source code to the files
46   you added to the patch.
47
48#. *Test Your Changes:* Once you have modified the source code, the
49   easiest way to test your changes is by calling the :ref:`ref-tasks-compile`
50   task as shown in the following example::
51
52      $ bitbake -c compile -f package
53
54   The ``-f`` or ``--force`` option forces the specified task to
55   execute. If you find problems with your code, you can just keep
56   editing and re-testing iteratively until things work as expected.
57
58   .. note::
59
60      All the modifications you make to the temporary source code disappear
61      once you run the :ref:`ref-tasks-clean` or :ref:`ref-tasks-cleanall`
62      tasks using BitBake (i.e. ``bitbake -c clean package`` and
63      ``bitbake -c cleanall package``). Modifications will also disappear if
64      you use the :ref:`ref-classes-rm-work` feature as described in
65      the ":ref:`dev-manual/disk-space:conserving disk space during builds`"
66      section.
67
68#. *Generate the Patch:* Once your changes work as expected, you need to
69   use Quilt to generate the final patch that contains all your
70   modifications::
71
72      $ quilt refresh
73
74   At this point, the
75   ``my_changes.patch`` file has all your edits made to the ``file1.c``,
76   ``file2.c``, and ``file3.c`` files.
77
78   You can find the resulting patch file in the ``patches/``
79   subdirectory of the source (:term:`S`) directory.
80
81#. *Copy the Patch File:* For simplicity, copy the patch file into a
82   directory named ``files``, which you can create in the same directory
83   that holds the recipe (``.bb``) file or the append (``.bbappend``)
84   file. Placing the patch here guarantees that the OpenEmbedded build
85   system will find the patch. Next, add the patch into the :term:`SRC_URI`
86   of the recipe. Here is an example::
87
88      SRC_URI += "file://my_changes.patch"
89
90