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1<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
2"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
3[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
4
5<chapter id='dev-manual-newbie'>
6
7<title>The Yocto Project Open Source Development Environment</title>
8
9<para>
10 This chapter helps you understand the Yocto Project as an open source development project.
11 In general, working in an open source environment is very different from working in a
12 closed, proprietary environment.
13 Additionally, the Yocto Project uses specific tools and constructs as part of its development
14 environment.
15 This chapter specifically addresses open source philosophy, using the
16 Yocto Project in a team environment, source repositories, Yocto Project
17 terms, licensing, the open source distributed version control system Git,
18 workflows, bug tracking, and how to submit changes.
19</para>
20
21<section id='open-source-philosophy'>
22 <title>Open Source Philosophy</title>
23
24 <para>
25 Open source philosophy is characterized by software development directed by peer production
26 and collaboration through an active community of developers.
27 Contrast this to the more standard centralized development models used by commercial software
28 companies where a finite set of developers produces a product for sale using a defined set
29 of procedures that ultimately result in an end product whose architecture and source material
30 are closed to the public.
31 </para>
32
33 <para>
34 Open source projects conceptually have differing concurrent agendas, approaches, and production.
35 These facets of the development process can come from anyone in the public (community) that has a
36 stake in the software project.
37 The open source environment contains new copyright, licensing, domain, and consumer issues
38 that differ from the more traditional development environment.
39 In an open source environment, the end product, source material, and documentation are
40 all available to the public at no cost.
41 </para>
42
43 <para>
44 A benchmark example of an open source project is the Linux kernel, which was initially conceived
45 and created by Finnish computer science student Linus Torvalds in 1991.
46 Conversely, a good example of a non-open source project is the
47 <trademark class='registered'>Windows</trademark> family of operating
48 systems developed by <trademark class='registered'>Microsoft</trademark> Corporation.
49 </para>
50
51 <para>
52 Wikipedia has a good historical description of the Open Source Philosophy
53 <ulink url='http://en.wikipedia.org/wiki/Open_source'>here</ulink>.
54 You can also find helpful information on how to participate in the Linux Community
55 <ulink url='http://ldn.linuxfoundation.org/book/how-participate-linux-community'>here</ulink>.
56 </para>
57</section>
58
59<section id="usingpoky-changes-collaborate">
60 <title>Using the Yocto Project in a Team Environment</title>
61
62 <para>
63 It might not be immediately clear how you can use the Yocto
64 Project in a team environment, or scale it for a large team of
65 developers.
66 One of the strengths of the Yocto Project is that it is extremely
67 flexible.
68 Thus, you can adapt it to many different use cases and scenarios.
69 However, these characteristics can cause a struggle if you are trying
70 to create a working setup that scales across a large team.
71 </para>
72
73 <para>
74 To help with these types of situations, this section presents
75 some of the project's most successful experiences,
76 practices, solutions, and available technologies that work well.
77 Keep in mind, the information here is a starting point.
78 You can build off it and customize it to fit any
79 particular working environment and set of practices.
80 </para>
81
82 <section id='best-practices-system-configurations'>
83 <title>System Configurations</title>
84
85 <para>
86 Systems across a large team should meet the needs of
87 two types of developers: those working on the contents of the
88 operating system image itself and those developing applications.
89 Regardless of the type of developer, their workstations must
90 be both reasonably powerful and run Linux.
91 </para>
92
93 <section id='best-practices-application-development'>
94 <title>Application Development</title>
95
96 <para>
97 For developers who mainly do application level work
98 on top of an existing software stack,
99 here are some practices that work best:
100 <itemizedlist>
101 <listitem><para>Use a pre-built toolchain that
102 contains the software stack itself.
103 Then, develop the application code on top of the
104 stack.
105 This method works well for small numbers of relatively
106 isolated applications.</para></listitem>
107 <listitem><para>When possible, use the Yocto Project
108 plug-in for the <trademark class='trade'>Eclipse</trademark> IDE
109 and other pieces of Application Development
110 Technology (ADT).
111 For more information, see the
112 "<link linkend='application-development-workflow'>Application
113 Development Workflow</link>" section as well as the
114 <ulink url='&YOCTO_DOCS_ADT_URL;'>Yocto Project Application Developer's Guide</ulink>.
115 </para></listitem>
116 <listitem><para>Keep your cross-development toolchains
117 updated.
118 You can do this through provisioning either as new
119 toolchain downloads or as updates through a package
120 update mechanism using <filename>opkg</filename>
121 to provide updates to an existing toolchain.
122 The exact mechanics of how and when to do this are a
123 question for local policy.</para></listitem>
124 <listitem><para>Use multiple toolchains installed locally
125 into different locations to allow development across
126 versions.</para></listitem>
127 </itemizedlist>
128 </para>
129 </section>
130
131 <section id='best-practices-core-system-development'>
132 <title>Core System Development</title>
133
134 <para>
135 For core system development, it is often best to have the
136 build system itself available on the developer workstations
137 so developers can run their own builds and directly
138 rebuild the software stack.
139 You should keep the core system unchanged as much as
140 possible and do your work in layers on top of the core system.
141 Doing so gives you a greater level of portability when
142 upgrading to new versions of the core system or Board
143 Support Packages (BSPs).
144 You can share layers amongst the developers of a particular
145 project and contain the policy configuration that defines
146 the project.
147 </para>
148
149 <para>
150 Aside from the previous best practices, there exists a number
151 of tips and tricks that can help speed up core development
152 projects:
153 <itemizedlist>
154 <listitem><para>Use a
155 <ulink url='&YOCTO_DOCS_REF_URL;#shared-state-cache'>Shared State Cache</ulink>
156 (sstate) among groups of developers who are on a
157 fast network.
158 The best way to share sstate is through a
159 Network File System (NFS) share.
160 The first user to build a given component for the
161 first time contributes that object to the sstate,
162 while subsequent builds from other developers then
163 reuse the object rather than rebuild it themselves.
164 </para>
165 <para>Although it is possible to use other protocols for the
166 sstate such as HTTP and FTP, you should avoid these.
167 Using HTTP limits the sstate to read-only and
168 FTP provides poor performance.
169 </para></listitem>
170 <listitem><para>Have autobuilders contribute to the sstate
171 pool similarly to how the developer workstations
172 contribute.
173 For information, see the
174 "<link linkend='best-practices-autobuilders'>Autobuilders</link>"
175 section.</para></listitem>
176 <listitem><para>Build stand-alone tarballs that contain
177 "missing" system requirements if for some reason
178 developer workstations do not meet minimum system
179 requirements such as latest Python versions,
180 <filename>chrpath</filename>, or other tools.
181 You can install and relocate the tarball exactly as you
182 would the usual cross-development toolchain so that
183 all developers can meet minimum version requirements
184 on most distributions.</para></listitem>
185 <listitem><para>Use a small number of shared,
186 high performance systems for testing purposes
187 (e.g. dual, six-core Xeons with 24 Gbytes of RAM
188 and plenty of disk space).
189 Developers can use these systems for wider, more
190 extensive testing while they continue to develop
191 locally using their primary development system.
192 </para></listitem>
193 <listitem><para>Enable the PR Service when package feeds
194 need to be incremental with continually increasing
195 <ulink url='&YOCTO_DOCS_REF_URL;#var-PR'>PR</ulink>
196 values.
197 Typically, this situation occurs when you use or
198 publish package feeds and use a shared state.
199 You should enable the PR Service for all users who
200 use the shared state pool.
201 For more information on the PR Service, see the
202 "<link linkend='working-with-a-pr-service'>Working With a PR Service</link>".
203 </para></listitem>
204 </itemizedlist>
205 </para>
206 </section>
207 </section>
208
209 <section id='best-practices-source-control-management'>
210 <title>Source Control Management (SCM)</title>
211
212 <para>
213 Keeping your
214 <ulink url='&YOCTO_DOCS_DEV_URL;#metadata'>Metadata</ulink>
215 and any software you are developing under the
216 control of an SCM system that is compatible
217 with the OpenEmbedded build system is advisable.
218 Of the SCMs BitBake supports, the
219 Yocto Project team strongly recommends using
220 <link linkend='git'>Git</link>.
221 Git is a distributed system that is easy to backup,
222 allows you to work remotely, and then connects back to the
223 infrastructure.
224 <note>
225 For information about BitBake, see the
226 <ulink url='&YOCTO_DOCS_BB_URL;'>BitBake User Manual</ulink>.
227 </note>
228 </para>
229
230 <para>
231 It is relatively easy to set up Git services and create
232 infrastructure like
233 <ulink url='&YOCTO_GIT_URL;'>http://git.yoctoproject.org</ulink>,
234 which is based on server software called
235 <filename>gitolite</filename> with <filename>cgit</filename>
236 being used to generate the web interface that lets you view the
237 repositories.
238 The <filename>gitolite</filename> software identifies users
239 using SSH keys and allows branch-based
240 access controls to repositories that you can control as little
241 or as much as necessary.
242 </para>
243
244 <note>
245 The setup of these services is beyond the scope of this manual.
246 However, sites such as these exist that describe how to perform
247 setup:
248 <itemizedlist>
249 <listitem><para><ulink url='http://git-scm.com/book/ch4-8.html'>Git documentation</ulink>:
250 Describes how to install <filename>gitolite</filename>
251 on the server.</para></listitem>
252 <listitem><para><ulink url='http://sitaramc.github.com/gitolite/master-toc.html'>The <filename>gitolite</filename> master index</ulink>:
253 All topics for <filename>gitolite</filename>.
254 </para></listitem>
255 <listitem><para><ulink url='https://git.wiki.kernel.org/index.php/Interfaces,_frontends,_and_tools'>Interfaces, frontends, and tools</ulink>:
256 Documentation on how to create interfaces and frontends
257 for Git.</para></listitem>
258 </itemizedlist>
259 </note>
260 </section>
261
262 <section id='best-practices-autobuilders'>
263 <title>Autobuilders</title>
264
265 <para>
266 Autobuilders are often the core of a development project.
267 It is here that changes from individual developers are brought
268 together and centrally tested and subsequent decisions about
269 releases can be made.
270 Autobuilders also allow for "continuous integration" style
271 testing of software components and regression identification
272 and tracking.
273 </para>
274
275 <para>
276 See "<ulink url='http://autobuilder.yoctoproject.org'>Yocto Project Autobuilder</ulink>"
277 for more information and links to buildbot.
278 The Yocto Project team has found this implementation
279 works well in this role.
280 A public example of this is the Yocto Project
281 Autobuilders, which we use to test the overall health of the
282 project.
283 </para>
284
285 <para>
286 The features of this system are:
287 <itemizedlist>
288 <listitem><para>Highlights when commits break the build.
289 </para></listitem>
290 <listitem><para>Populates an sstate cache from which
291 developers can pull rather than requiring local
292 builds.</para></listitem>
293 <listitem><para>Allows commit hook triggers,
294 which trigger builds when commits are made.
295 </para></listitem>
296 <listitem><para>Allows triggering of automated image booting
297 and testing under the QuickEMUlator (QEMU).
298 </para></listitem>
299 <listitem><para>Supports incremental build testing and
300 from-scratch builds.</para></listitem>
301 <listitem><para>Shares output that allows developer
302 testing and historical regression investigation.
303 </para></listitem>
304 <listitem><para>Creates output that can be used for releases.
305 </para></listitem>
306 <listitem><para>Allows scheduling of builds so that resources
307 can be used efficiently.</para></listitem>
308 </itemizedlist>
309 </para>
310 </section>
311
312 <section id='best-practices-policies-and-change-flow'>
313 <title>Policies and Change Flow</title>
314
315 <para>
316 The Yocto Project itself uses a hierarchical structure and a
317 pull model.
318 Scripts exist to create and send pull requests
319 (i.e. <filename>create-pull-request</filename> and
320 <filename>send-pull-request</filename>).
321 This model is in line with other open source projects where
322 maintainers are responsible for specific areas of the project
323 and a single maintainer handles the final "top-of-tree" merges.
324 </para>
325
326 <note>
327 You can also use a more collective push model.
328 The <filename>gitolite</filename> software supports both the
329 push and pull models quite easily.
330 </note>
331
332 <para>
333 As with any development environment, it is important
334 to document the policy used as well as any main project
335 guidelines so they are understood by everyone.
336 It is also a good idea to have well structured
337 commit messages, which are usually a part of a project's
338 guidelines.
339 Good commit messages are essential when looking back in time and
340 trying to understand why changes were made.
341 </para>
342
343 <para>
344 If you discover that changes are needed to the core layer of the
345 project, it is worth sharing those with the community as soon
346 as possible.
347 Chances are if you have discovered the need for changes, someone
348 else in the community needs them also.
349 </para>
350 </section>
351
352 <section id='best-practices-summary'>
353 <title>Summary</title>
354
355 <para>
356 This section summarizes the key recommendations described in the
357 previous sections:
358 <itemizedlist>
359 <listitem><para>Use <link linkend='git'>Git</link>
360 as the source control system.</para></listitem>
361 <listitem><para>Maintain your Metadata in layers that make sense
362 for your situation.
363 See the "<link linkend='understanding-and-creating-layers'>Understanding
364 and Creating Layers</link>" section for more information on
365 layers.</para></listitem>
366 <listitem><para>
367 Separate the project's Metadata and code by using
368 separate Git repositories.
369 See the
370 "<link linkend='yocto-project-repositories'>Yocto Project Source Repositories</link>"
371 section for information on these repositories.
372 See the
373 "<link linkend='getting-setup'>Getting Set Up</link>"
374 section for information on how to set up local Git
375 repositories for related upstream Yocto Project
376 Git repositories.
377 </para></listitem>
378 <listitem><para>Set up the directory for the shared state cache
379 (<ulink url='&YOCTO_DOCS_REF_URL;#var-SSTATE_DIR'><filename>SSTATE_DIR</filename></ulink>)
380 where it makes sense.
381 For example, set up the sstate cache on a system used
382 by developers in the same organization and share the
383 same source directories on their machines.
384 </para></listitem>
385 <listitem><para>Set up an Autobuilder and have it populate the
386 sstate cache and source directories.</para></listitem>
387 <listitem><para>The Yocto Project community encourages you
388 to send patches to the project to fix bugs or add features.
389 If you do submit patches, follow the project commit
390 guidelines for writing good commit messages.
391 See the "<link linkend='how-to-submit-a-change'>How to Submit a Change</link>"
392 section.</para></listitem>
393 <listitem><para>Send changes to the core sooner than later
394 as others are likely to run into the same issues.
395 For some guidance on mailing lists to use, see the list in the
396 "<link linkend='how-to-submit-a-change'>How to Submit a Change</link>"
397 section.
398 For a description of the available mailing lists, see the
399 "<ulink url='&YOCTO_DOCS_REF_URL;#resources-mailinglist'>Mailing Lists</ulink>"
400 section in the Yocto Project Reference Manual.
401 </para></listitem>
402 </itemizedlist>
403 </para>
404 </section>
405</section>
406
407<section id='yocto-project-repositories'>
408 <title>Yocto Project Source Repositories</title>
409
410 <para>
411 The Yocto Project team maintains complete source repositories for all
412 Yocto Project files at
413 <ulink url='&YOCTO_GIT_URL;/cgit/cgit.cgi'></ulink>.
414 This web-based source code browser is organized into categories by
415 function such as IDE Plugins, Matchbox, Poky, Yocto Linux Kernel, and
416 so forth.
417 From the interface, you can click on any particular item in the "Name"
418 column and see the URL at the bottom of the page that you need to clone
419 a Git repository for that particular item.
420 Having a local Git repository of the
421 <link linkend='source-directory'>Source Directory</link>, which is
422 usually named "poky", allows
423 you to make changes, contribute to the history, and ultimately enhance
424 the Yocto Project's tools, Board Support Packages, and so forth.
425 </para>
426
427 <para>
428 For any supported release of Yocto Project, you can also go to the
429 <ulink url='&YOCTO_HOME_URL;'>Yocto Project Website</ulink> and
430 select the "Downloads" tab and get a released tarball of the
431 <filename>poky</filename> repository or any supported BSP tarballs.
432 Unpacking these tarballs gives you a snapshot of the released
433 files.
434 <note><title>Notes</title>
435 <itemizedlist>
436 <listitem><para>
437 The recommended method for setting up the Yocto Project
438 <link linkend='source-directory'>Source Directory</link>
439 and the files for supported BSPs
440 (e.g., <filename>meta-intel</filename>) is to use
441 <link linkend='git'>Git</link> to create a local copy of
442 the upstream repositories.
443 </para></listitem>
444 <listitem><para>
445 Be sure to always work in matching branches for both
446 the selected BSP repository and the
447 <link linkend='source-directory'>Source Directory</link>
448 (i.e. <filename>poky</filename>) repository.
449 For example, if you have checked out the "master" branch
450 of <filename>poky</filename> and you are going to use
451 <filename>meta-intel</filename>, be sure to checkout the
452 "master" branch of <filename>meta-intel</filename>.
453 </para></listitem>
454 </itemizedlist>
455 </note>
456 </para>
457
458 <para>
459 In summary, here is where you can get the project files needed for development:
460 <itemizedlist>
461 <listitem><para id='source-repositories'><emphasis><ulink url='&YOCTO_GIT_URL;/cgit/cgit.cgi'>Source Repositories:</ulink></emphasis>
462 This area contains IDE Plugins, Matchbox, Poky, Poky Support, Tools, Yocto Linux Kernel, and Yocto
463 Metadata Layers.
464 You can create local copies of Git repositories for each of these areas.</para>
465 <para>
466 <imagedata fileref="figures/source-repos.png" align="center" width="6in" depth="4in" />
467 </para></listitem>
468 <listitem><para><anchor id='index-downloads' /><emphasis><ulink url='&YOCTO_DL_URL;/releases/'>Index of /releases:</ulink></emphasis>
469 This is an index of releases such as
470 the <trademark class='trade'>Eclipse</trademark>
471 Yocto Plug-in, miscellaneous support, Poky, Pseudo, installers for cross-development toolchains,
472 and all released versions of Yocto Project in the form of images or tarballs.
473 Downloading and extracting these files does not produce a local copy of the
474 Git repository but rather a snapshot of a particular release or image.</para>
475 <para>
476 <imagedata fileref="figures/index-downloads.png" align="center" width="6in" depth="3.5in" />
477 </para></listitem>
478 <listitem><para><emphasis>"Downloads" page for the
479 <ulink url='&YOCTO_HOME_URL;'>Yocto Project Website</ulink>:</emphasis>
480 Access this page by going to the website and then selecting
481 the "Downloads" tab.
482 This page allows you to download any Yocto Project
483 release or Board Support Package (BSP) in tarball form.
484 The tarballs are similar to those found in the
485 <ulink url='&YOCTO_DL_URL;/releases/'>Index of /releases:</ulink> area.</para>
486 <para>
487 <imagedata fileref="figures/yp-download.png" align="center" width="6in" depth="4in" />
488 </para></listitem>
489 </itemizedlist>
490 </para>
491</section>
492
493<section id='yocto-project-terms'>
494 <title>Yocto Project Terms</title>
495
496 <para>
497 Following is a list of terms and definitions users new to the Yocto Project development
498 environment might find helpful.
499 While some of these terms are universal, the list includes them just in case:
500 <itemizedlist>
501 <listitem><para><emphasis>Append Files:</emphasis> Files that append build information to
502 a recipe file.
503 Append files are known as BitBake append files and <filename>.bbappend</filename> files.
504 The OpenEmbedded build system expects every append file to have a corresponding
505 recipe (<filename>.bb</filename>) file.
506 Furthermore, the append file and corresponding recipe file
507 must use the same root filename.
508 The filenames can differ only in the file type suffix used (e.g.
509 <filename>formfactor_0.0.bb</filename> and <filename>formfactor_0.0.bbappend</filename>).
510 </para>
511 <para>Information in append files extends or overrides the
512 information in the similarly-named recipe file.
513 For an example of an append file in use, see the
514 "<link linkend='using-bbappend-files'>Using .bbappend Files</link>" section.
515 <note>
516 Append files can also use wildcard patterns in their version numbers
517 so they can be applied to more than one version of the underlying recipe file.
518 </note>
519 </para></listitem>
520 <listitem><para id='bitbake-term'><emphasis>BitBake:</emphasis>
521 The task executor and scheduler used by the OpenEmbedded build
522 system to build images.
523 For more information on BitBake, see the
524 <ulink url='&YOCTO_DOCS_BB_URL;'>BitBake User Manual</ulink>.
525 </para></listitem>
526 <listitem>
527 <para id='build-directory'><emphasis>Build Directory:</emphasis>
528 This term refers to the area used by the OpenEmbedded build
529 system for builds.
530 The area is created when you <filename>source</filename> the
531 setup environment script that is found in the Source Directory
532 (i.e. <ulink url='&YOCTO_DOCS_REF_URL;#structure-core-script'><filename>&OE_INIT_FILE;</filename></ulink>
533 or
534 <ulink url='&YOCTO_DOCS_REF_URL;#structure-memres-core-script'><filename>oe-init-build-env-memres</filename></ulink>).
535 The <ulink url='&YOCTO_DOCS_REF_URL;#var-TOPDIR'><filename>TOPDIR</filename></ulink>
536 variable points to the Build Directory.</para>
537
538 <para>
539 You have a lot of flexibility when creating the Build
540 Directory.
541 Following are some examples that show how to create the
542 directory.
543 The examples assume your
544 <link linkend='source-directory'>Source Directory</link> is
545 named <filename>poky</filename>:
546 <itemizedlist>
547 <listitem><para>Create the Build Directory inside your
548 Source Directory and let the name of the Build
549 Directory default to <filename>build</filename>:
550 <literallayout class='monospaced'>
551 $ cd $HOME/poky
552 $ source &OE_INIT_FILE;
553 </literallayout></para></listitem>
554 <listitem><para>Create the Build Directory inside your
555 home directory and specifically name it
556 <filename>test-builds</filename>:
557 <literallayout class='monospaced'>
558 $ cd $HOME
559 $ source poky/&OE_INIT_FILE; test-builds
560 </literallayout></para></listitem>
561 <listitem><para>
562 Provide a directory path and
563 specifically name the Build Directory.
564 Any intermediate folders in the pathname must
565 exist.
566 This next example creates a Build Directory named
567 <filename>YP-&POKYVERSION;</filename>
568 in your home directory within the existing
569 directory <filename>mybuilds</filename>:
570 <literallayout class='monospaced'>
571 $cd $HOME
572 $ source $HOME/poky/&OE_INIT_FILE; $HOME/mybuilds/YP-&POKYVERSION;
573 </literallayout></para></listitem>
574 </itemizedlist>
575 <note>
576 By default, the Build Directory contains
577 <ulink url='&YOCTO_DOCS_REF_URL;#var-TMPDIR'><filename>TMPDIR</filename></ulink>,
578 which is a temporary directory the build system uses for
579 its work.
580 <filename>TMPDIR</filename> cannot be under NFS.
581 Thus, by default, the Build Directory cannot be under NFS.
582 However, if you need the Build Directory to be under NFS,
583 you can set this up by setting <filename>TMPDIR</filename>
584 in your <filename>local.conf</filename> file
585 to use a local drive.
586 Doing so effectively separates <filename>TMPDIR</filename>
587 from <filename>TOPDIR</filename>, which is the Build
588 Directory.
589 </note>
590 </para></listitem>
591 <listitem><para id='build-system-term'><emphasis>Build System:</emphasis>
592 In the context of the Yocto Project,
593 this term refers to the OpenEmbedded build system used by the project.
594 This build system is based on the project known as "Poky."
595 For some historical information about Poky, see the
596 <link linkend='poky'>Poky</link> term.
597 </para></listitem>
598 <listitem><para><emphasis>Classes:</emphasis> Files that provide for logic encapsulation
599 and inheritance so that commonly used patterns can be defined once and then easily used
600 in multiple recipes.
601 For reference information on the Yocto Project classes, see the
602 "<ulink url='&YOCTO_DOCS_REF_URL;#ref-classes'>Classes</ulink>" chapter of the
603 Yocto Project Reference Manual.
604 Class files end with the <filename>.bbclass</filename> filename extension.
605 </para></listitem>
606 <listitem><para><emphasis>Configuration File:</emphasis>
607 Configuration information in various <filename>.conf</filename>
608 files provides global definitions of variables.
609 The <filename>conf/local.conf</filename> configuration file in
610 the
611 <link linkend='build-directory'>Build Directory</link>
612 contains user-defined variables that affect every build.
613 The <filename>meta-yocto/conf/distro/poky.conf</filename>
614 configuration file defines Yocto "distro" configuration
615 variables used only when building with this policy.
616 Machine configuration files, which
617 are located throughout the
618 <link linkend='source-directory'>Source Directory</link>, define
619 variables for specific hardware and are only used when building
620 for that target (e.g. the
621 <filename>machine/beaglebone.conf</filename> configuration
622 file defines variables for the Texas Instruments ARM Cortex-A8
623 development board).
624 Configuration files end with a <filename>.conf</filename>
625 filename extension.
626 </para></listitem>
627 <listitem><para id='cross-development-toolchain'>
628 <emphasis>Cross-Development Toolchain:</emphasis>
629 In general, a cross-development toolchain is a collection of
630 software development tools and utilities that run on one
631 architecture and allow you to develop software for a
632 different, or targeted, architecture.
633 These toolchains contain cross-compilers, linkers, and
634 debuggers that are specific to the target architecture.
635 </para>
636
637 <para>The Yocto Project supports two different cross-development
638 toolchains:
639 <itemizedlist>
640 <listitem><para>A toolchain only used by and within
641 BitBake when building an image for a target
642 architecture.</para></listitem>
643 <listitem><para>A relocatable toolchain used outside of
644 BitBake by developers when developing applications
645 that will run on a targeted device.
646 Sometimes this relocatable cross-development
647 toolchain is referred to as the meta-toolchain.
648 </para></listitem>
649 </itemizedlist>
650 </para>
651
652 <para>
653 Creation of these toolchains is simple and automated.
654 For information on toolchain concepts as they apply to the
655 Yocto Project, see the
656 "<ulink url='&YOCTO_DOCS_REF_URL;#cross-development-toolchain-generation'>Cross-Development Toolchain Generation</ulink>"
657 section in the Yocto Project Reference Manual.
658 You can also find more information on using the
659 relocatable toolchain in the
660 <ulink url='&YOCTO_DOCS_ADT_URL;'>Yocto Project
661 Application Developer's Guide</ulink>.
662 </para></listitem>
663 <listitem><para><emphasis>Image:</emphasis>
664 An image is an artifact of the BitBake build process given
665 a collection of recipes and related Metadata.
666 Images are the binary output that run on specific hardware or
667 QEMU and are used for specific use-cases.
668 For a list of the supported image types that the Yocto Project provides, see the
669 "<ulink url='&YOCTO_DOCS_REF_URL;#ref-images'>Images</ulink>"
670 chapter in the Yocto Project Reference Manual.</para></listitem>
671 <listitem><para id='layer'><emphasis>Layer:</emphasis> A collection of recipes representing the core,
672 a BSP, or an application stack.
673 For a discussion specifically on BSP Layers, see the
674 "<ulink url='&YOCTO_DOCS_BSP_URL;#bsp-layers'>BSP Layers</ulink>"
675 section in the Yocto Project Board Support Packages (BSP)
676 Developer's Guide.</para></listitem>
677 <listitem><para id='meta-toolchain'><emphasis>Meta-Toolchain:</emphasis>
678 A term sometimes used for
679 <link linkend='cross-development-toolchain'>Cross-Development Toolchain</link>.
680 </para></listitem>
681 <listitem><para id='metadata'><emphasis>Metadata:</emphasis>
682 The files that BitBake parses when building an image.
683 In general, Metadata includes recipes, classes, and
684 configuration files.
685 In the context of the kernel ("kernel Metadata"),
686 it refers to Metadata in the <filename>meta</filename>
687 branches of the kernel source Git repositories.
688 </para></listitem>
689 <listitem><para id='oe-core'><emphasis>OE-Core:</emphasis> A core set of Metadata originating
690 with OpenEmbedded (OE) that is shared between OE and the Yocto Project.
691 This Metadata is found in the <filename>meta</filename> directory of the
692 <link linkend='source-directory'>Source Directory</link>.</para></listitem>
693 <listitem><para><emphasis>Package:</emphasis>
694 In the context of the Yocto Project, this term refers to a
695 recipe's packaged output produced by BitBake (i.e. a
696 "baked recipe").
697 A package is generally the compiled binaries produced from the
698 recipe's sources.
699 You "bake" something by running it through BitBake.</para>
700 <para>It is worth noting that the term "package" can, in general, have subtle
701 meanings. For example, the packages referred to in the
702 "<ulink url='&YOCTO_DOCS_QS_URL;#packages'>The Packages</ulink>" section are
703 compiled binaries that, when installed, add functionality to your Linux
704 distribution.</para>
705 <para>Another point worth noting is that historically within the Yocto Project,
706 recipes were referred to as packages - thus, the existence of several BitBake
707 variables that are seemingly mis-named,
708 (e.g. <ulink url='&YOCTO_DOCS_REF_URL;#var-PR'><filename>PR</filename></ulink>,
709 <ulink url='&YOCTO_DOCS_REF_URL;#var-PV'><filename>PV</filename></ulink>, and
710 <ulink url='&YOCTO_DOCS_REF_URL;#var-PE'><filename>PE</filename></ulink>).
711 </para></listitem>
712 <listitem><para><emphasis>Package Groups:</emphasis>
713 Arbitrary groups of software Recipes.
714 You use package groups to hold recipes that, when built,
715 usually accomplish a single task.
716 For example, a package group could contain the recipes for a
717 company’s proprietary or value-add software.
718 Or, the package group could contain the recipes that enable
719 graphics.
720 A package group is really just another recipe.
721 Because package group files are recipes, they end with the
722 <filename>.bb</filename> filename extension.</para></listitem>
723 <listitem><para id='poky'><emphasis>Poky:</emphasis> The term "poky" can mean several things.
724 In its most general sense, it is an open-source project that was initially developed
725 by OpenedHand. With OpenedHand, poky was developed off of the existing OpenEmbedded
726 build system becoming a build system for embedded images.
727 After Intel Corporation acquired OpenedHand, the project poky became the basis for
728 the Yocto Project's build system.</para>
729 <para>
730 Within the Yocto Project source repositories, <filename>poky</filename>
731 exists as a separate Git repository
732 that can be cloned to yield a local copy on the host system.
733 Thus, "poky" can refer to the local copy of the Source Directory used to develop within
734 the Yocto Project.</para></listitem>
735 <listitem><para><emphasis>Recipe:</emphasis>
736 A set of instructions for building packages.
737 A recipe describes where you get source code, which patches
738 to apply, how to configure the source, how to compile it and so on.
739 Recipes also describe dependencies for libraries or for other
740 recipes.
741 Recipes represent the logical unit of execution, the software
742 to build, the images to build, and use the
743 <filename>.bb</filename> file extension.
744 </para></listitem>
745 <listitem>
746 <para id='source-directory'><emphasis>Source Directory:</emphasis>
747 This term refers to the directory structure created as a result
748 of creating a local copy of the <filename>poky</filename> Git
749 repository <filename>git://git.yoctoproject.org/poky</filename>
750 or expanding a released <filename>poky</filename> tarball.
751 <note>
752 Creating a local copy of the <filename>poky</filename>
753 Git repository is the recommended method for setting up
754 your Source Directory.
755 </note>
756 Sometimes you might hear the term "poky directory" used to refer
757 to this directory structure.
758 <note>
759 The OpenEmbedded build system does not support file or
760 directory names that contain spaces.
761 Be sure that the Source Directory you use does not contain
762 these types of names.
763 </note></para>
764
765 <para>The Source Directory contains BitBake, Documentation,
766 Metadata and other files that all support the Yocto Project.
767 Consequently, you must have the Source Directory in place on
768 your development system in order to do any development using
769 the Yocto Project.</para>
770
771 <para>When you create a local copy of the Git repository, you
772 can name the repository anything you like.
773 Throughout much of the documentation, "poky"
774 is used as the name of the top-level folder of the local copy of
775 the poky Git repository.
776 So, for example, cloning the <filename>poky</filename> Git
777 repository results in a local Git repository whose top-level
778 folder is also named "poky".</para>
779
780 <para>While it is not recommended that you use tarball expansion
781 to set up the Source Directory, if you do, the top-level
782 directory name of the Source Directory is derived from the
783 Yocto Project release tarball.
784 For example, downloading and unpacking
785 <filename>&YOCTO_POKY_TARBALL;</filename> results in a
786 Source Directory whose root folder is named
787 <filename>&YOCTO_POKY;</filename>.</para>
788
789 <para>It is important to understand the differences between the
790 Source Directory created by unpacking a released tarball as
791 compared to cloning
792 <filename>git://git.yoctoproject.org/poky</filename>.
793 When you unpack a tarball, you have an exact copy of the files
794 based on the time of release - a fixed release point.
795 Any changes you make to your local files in the Source Directory
796 are on top of the release and will remain local only.
797 On the other hand, when you clone the <filename>poky</filename>
798 Git repository, you have an active development repository with
799 access to the upstream repository's branches and tags.
800 In this case, any local changes you make to the local
801 Source Directory can be later applied to active development
802 branches of the upstream <filename>poky</filename> Git
803 repository.</para>
804
805 <para>For more information on concepts related to Git
806 repositories, branches, and tags, see the
807 "<link linkend='repositories-tags-and-branches'>Repositories, Tags, and Branches</link>"
808 section.</para></listitem>
809 <listitem><para><emphasis>Task:</emphasis>
810 A unit of execution for BitBake (e.g.
811 <ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-compile'><filename>do_compile</filename></ulink>,
812 <ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-fetch'><filename>do_fetch</filename></ulink>,
813 <ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-patch'><filename>do_patch</filename></ulink>,
814 and so forth).
815 </para></listitem>
816 <listitem><para><emphasis>Upstream:</emphasis> A reference to source code or repositories
817 that are not local to the development system but located in a master area that is controlled
818 by the maintainer of the source code.
819 For example, in order for a developer to work on a particular piece of code, they need to
820 first get a copy of it from an "upstream" source.</para></listitem>
821 </itemizedlist>
822 </para>
823</section>
824
825<section id='licensing'>
826 <title>Licensing</title>
827
828 <para>
829 Because open source projects are open to the public, they have different licensing structures in place.
830 License evolution for both Open Source and Free Software has an interesting history.
831 If you are interested in this history, you can find basic information here:
832 <itemizedlist>
833 <listitem><para><ulink url='http://en.wikipedia.org/wiki/Open-source_license'>Open source license history</ulink>
834 </para></listitem>
835 <listitem><para><ulink url='http://en.wikipedia.org/wiki/Free_software_license'>Free software license
836 history</ulink></para></listitem>
837 </itemizedlist>
838 </para>
839
840 <para>
841 In general, the Yocto Project is broadly licensed under the Massachusetts Institute of Technology
842 (MIT) License.
843 MIT licensing permits the reuse of software within proprietary software as long as the
844 license is distributed with that software.
845 MIT is also compatible with the GNU General Public License (GPL).
846 Patches to the Yocto Project follow the upstream licensing scheme.
847 You can find information on the MIT license
848 <ulink url='http://www.opensource.org/licenses/mit-license.php'>here</ulink>.
849 You can find information on the GNU GPL <ulink url='http://www.opensource.org/licenses/LGPL-3.0'>
850 here</ulink>.
851 </para>
852
853 <para>
854 When you build an image using the Yocto Project, the build process uses a
855 known list of licenses to ensure compliance.
856 You can find this list in the
857 <link linkend='source-directory'>Source Directory</link> at
858 <filename>meta/files/common-licenses</filename>.
859 Once the build completes, the list of all licenses found and used during that build are
860 kept in the
861 <link linkend='build-directory'>Build Directory</link> at
862 <filename>tmp/deploy/licenses</filename>.
863 </para>
864
865 <para>
866 If a module requires a license that is not in the base list, the build process
867 generates a warning during the build.
868 These tools make it easier for a developer to be certain of the licenses with which
869 their shipped products must comply.
870 However, even with these tools it is still up to the developer to resolve potential licensing issues.
871 </para>
872
873 <para>
874 The base list of licenses used by the build process is a combination of the Software Package
875 Data Exchange (SPDX) list and the Open Source Initiative (OSI) projects.
876 <ulink url='http://spdx.org'>SPDX Group</ulink> is a working group of the Linux Foundation
877 that maintains a specification
878 for a standard format for communicating the components, licenses, and copyrights
879 associated with a software package.
880 <ulink url='http://opensource.org'>OSI</ulink> is a corporation dedicated to the Open Source
881 Definition and the effort for reviewing and approving licenses that
882 conform to the Open Source Definition (OSD).
883 </para>
884
885 <para>
886 You can find a list of the combined SPDX and OSI licenses that the
887 Yocto Project uses in the
888 <filename>meta/files/common-licenses</filename> directory in your
889 <link linkend='source-directory'>Source Directory</link>.
890 </para>
891
892 <para>
893 For information that can help you maintain compliance with various
894 open source licensing during the lifecycle of a product created using
895 the Yocto Project, see the
896 "<link linkend='maintaining-open-source-license-compliance-during-your-products-lifecycle'>Maintaining Open Source License Compliance During Your Product's Lifecycle</link>"
897 section.
898 </para>
899</section>
900
901<section id='git'>
902 <title>Git</title>
903
904 <para>
905 The Yocto Project makes extensive use of Git,
906 which is a free, open source distributed version control system.
907 Git supports distributed development, non-linear development, and can handle large projects.
908 It is best that you have some fundamental understanding of how Git tracks projects and
909 how to work with Git if you are going to use the Yocto Project for development.
910 This section provides a quick overview of how Git works and provides you with a summary
911 of some essential Git commands.
912 </para>
913
914 <para>
915 For more information on Git, see
916 <ulink url='http://git-scm.com/documentation'></ulink>.
917 If you need to download Git, go to <ulink url='http://git-scm.com/download'></ulink>.
918 </para>
919
920 <section id='repositories-tags-and-branches'>
921 <title>Repositories, Tags, and Branches</title>
922
923 <para>
924 As mentioned earlier in the section
925 "<link linkend='yocto-project-repositories'>Yocto Project Source Repositories</link>",
926 the Yocto Project maintains source repositories at
927 <ulink url='&YOCTO_GIT_URL;/cgit.cgi'></ulink>.
928 If you look at this web-interface of the repositories, each item is a separate
929 Git repository.
930 </para>
931
932 <para>
933 Git repositories use branching techniques that track content change (not files)
934 within a project (e.g. a new feature or updated documentation).
935 Creating a tree-like structure based on project divergence allows for excellent historical
936 information over the life of a project.
937 This methodology also allows for an environment from which you can do lots of
938 local experimentation on projects as you develop changes or new features.
939 </para>
940
941 <para>
942 A Git repository represents all development efforts for a given project.
943 For example, the Git repository <filename>poky</filename> contains all changes
944 and developments for Poky over the course of its entire life.
945 That means that all changes that make up all releases are captured.
946 The repository maintains a complete history of changes.
947 </para>
948
949 <para>
950 You can create a local copy of any repository by "cloning" it with the Git
951 <filename>clone</filename> command.
952 When you clone a Git repository, you end up with an identical copy of the
953 repository on your development system.
954 Once you have a local copy of a repository, you can take steps to develop locally.
955 For examples on how to clone Git repositories, see the
956 "<link linkend='getting-setup'>Getting Set Up</link>" section.
957 </para>
958
959 <para>
960 It is important to understand that Git tracks content change and
961 not files.
962 Git uses "branches" to organize different development efforts.
963 For example, the <filename>poky</filename> repository has
964 <filename>denzil</filename>, <filename>danny</filename>,
965 <filename>dylan</filename>, <filename>dora</filename>,
966 <filename>daisy</filename>, and <filename>master</filename> branches
967 among others.
968 You can see all the branches by going to
969 <ulink url='&YOCTO_GIT_URL;/cgit.cgi/poky/'></ulink> and
970 clicking on the
971 <filename><ulink url='&YOCTO_GIT_URL;/cgit.cgi/poky/refs/heads'>[...]</ulink></filename>
972 link beneath the "Branch" heading.
973 </para>
974
975 <para>
976 Each of these branches represents a specific area of development.
977 The <filename>master</filename> branch represents the current or most recent
978 development.
979 All other branches represent offshoots of the <filename>master</filename>
980 branch.
981 </para>
982
983 <para>
984 When you create a local copy of a Git repository, the copy has the same set
985 of branches as the original.
986 This means you can use Git to create a local working area (also called a branch)
987 that tracks a specific development branch from the source Git repository.
988 in other words, you can define your local Git environment to work on any development
989 branch in the repository.
990 To help illustrate, here is a set of commands that creates a local copy of the
991 <filename>poky</filename> Git repository and then creates and checks out a local
992 Git branch that tracks the Yocto Project &DISTRO; Release (&DISTRO_NAME;) development:
993 <literallayout class='monospaced'>
994 $ cd ~
995 $ git clone git://git.yoctoproject.org/poky
996 $ cd poky
997 $ git checkout -b &DISTRO_NAME; origin/&DISTRO_NAME;
998 </literallayout>
999 In this example, the name of the top-level directory of your local
1000 <link linkend='source-directory'>Source Directory</link>
1001 is "poky" and the name of that local working area (local branch)
1002 you just created and checked out is "&DISTRO_NAME;".
1003 The files in your local repository now reflect the same files that
1004 are in the "&DISTRO_NAME;" development branch of the
1005 Yocto Project's "poky" upstream repository.
1006 It is important to understand that when you create and checkout a
1007 local working branch based on a branch name,
1008 your local environment matches the "tip" of that development branch
1009 at the time you created your local branch, which could be
1010 different from the files at the time of a similarly named release.
1011 In other words, creating and checking out a local branch based on
1012 the "&DISTRO_NAME;" branch name is not the same as
1013 cloning and checking out the "master" branch.
1014 Keep reading to see how you create a local snapshot of a Yocto
1015 Project Release.
1016 </para>
1017
1018 <para>
1019 Git uses "tags" to mark specific changes in a repository.
1020 Typically, a tag is used to mark a special point such as the final
1021 change before a project is released.
1022 You can see the tags used with the <filename>poky</filename> Git
1023 repository by going to
1024 <ulink url='&YOCTO_GIT_URL;/cgit.cgi/poky/'></ulink> and
1025 clicking on the
1026 <filename><ulink url='&YOCTO_GIT_URL;/cgit.cgi/poky/refs/tags'>[...]</ulink></filename>
1027 link beneath the "Tag" heading.
1028 </para>
1029
1030 <para>
1031 Some key tags are <filename>dylan-9.0.0</filename>,
1032 <filename>dora-10.0.0</filename>, <filename>daisy-11.0.0</filename>,
1033 and <filename>&DISTRO_NAME;-&POKYVERSION;</filename>.
1034 These tags represent Yocto Project releases.
1035 </para>
1036
1037 <para>
1038 When you create a local copy of the Git repository, you also have access to all the
1039 tags.
1040 Similar to branches, you can create and checkout a local working Git branch based
1041 on a tag name.
1042 When you do this, you get a snapshot of the Git repository that reflects
1043 the state of the files when the change was made associated with that tag.
1044 The most common use is to checkout a working branch that matches a specific
1045 Yocto Project release.
1046 Here is an example:
1047 <literallayout class='monospaced'>
1048 $ cd ~
1049 $ git clone git://git.yoctoproject.org/poky
1050 $ cd poky
1051 $ git checkout -b my-&DISTRO_NAME;-&POKYVERSION; &DISTRO_NAME;-&POKYVERSION;
1052 </literallayout>
1053 In this example, the name of the top-level directory of your local Yocto Project
1054 Files Git repository is <filename>poky</filename>.
1055 And, the name of the local branch you have created and checked out is
1056 <filename>my-&DISTRO_NAME;-&POKYVERSION;</filename>.
1057 The files in your repository now exactly match the Yocto Project &DISTRO;
1058 Release tag (<filename>&DISTRO_NAME;-&POKYVERSION;</filename>).
1059 It is important to understand that when you create and checkout a local
1060 working branch based on a tag, your environment matches a specific point
1061 in time and not the entire development branch.
1062 </para>
1063 </section>
1064
1065 <section id='basic-commands'>
1066 <title>Basic Commands</title>
1067
1068 <para>
1069 Git has an extensive set of commands that lets you manage changes and perform
1070 collaboration over the life of a project.
1071 Conveniently though, you can manage with a small set of basic operations and workflows
1072 once you understand the basic philosophy behind Git.
1073 You do not have to be an expert in Git to be functional.
1074 A good place to look for instruction on a minimal set of Git commands is
1075 <ulink url='http://git-scm.com/documentation'>here</ulink>.
1076 If you need to download Git, you can do so
1077 <ulink url='http://git-scm.com/download'>here</ulink>.
1078 </para>
1079
1080 <para>
1081 If you do not know much about Git, you should educate
1082 yourself by visiting the links previously mentioned.
1083 </para>
1084
1085 <para>
1086 The following list briefly describes some basic Git operations as a way to get started.
1087 As with any set of commands, this list (in most cases) simply shows the base command and
1088 omits the many arguments they support.
1089 See the Git documentation for complete descriptions and strategies on how to use these commands:
1090 <itemizedlist>
1091 <listitem><para><emphasis><filename>git init</filename>:</emphasis> Initializes an empty Git repository.
1092 You cannot use Git commands unless you have a <filename>.git</filename> repository.</para></listitem>
1093 <listitem><para><emphasis><filename>git clone</filename>:</emphasis>
1094 Creates a local clone of a Git repository.
1095 During collaboration, this command allows you to create a
1096 local Git repository that is on equal footing with a fellow
1097 developer’s Git repository.
1098 </para></listitem>
1099 <listitem><para><emphasis><filename>git add</filename>:</emphasis> Stages updated file contents
1100 to the index that
1101 Git uses to track changes.
1102 You must stage all files that have changed before you can commit them.</para></listitem>
1103 <listitem><para><emphasis><filename>git commit</filename>:</emphasis> Creates a "commit" that documents
1104 the changes you made.
1105 Commits are used for historical purposes, for determining if a maintainer of a project
1106 will allow the change, and for ultimately pushing the change from your local Git repository
1107 into the project’s upstream (or master) repository.</para></listitem>
1108 <listitem><para><emphasis><filename>git status</filename>:</emphasis> Reports any modified files that
1109 possibly need to be staged and committed.</para></listitem>
1110 <listitem><para><emphasis><filename>git checkout &lt;branch-name&gt;</filename>:</emphasis> Changes
1111 your working branch.
1112 This command is analogous to "cd".</para></listitem>
1113 <listitem><para><emphasis><filename>git checkout –b &lt;working-branch&gt;</filename>:</emphasis> Creates
1114 a working branch on your local machine where you can isolate work.
1115 It is a good idea to use local branches when adding specific features or changes.
1116 This way if you do not like what you have done you can easily get rid of the work.</para></listitem>
1117 <listitem><para><emphasis><filename>git branch</filename>:</emphasis> Reports
1118 existing local branches and
1119 tells you the branch in which you are currently working.</para></listitem>
1120 <listitem><para><emphasis><filename>git branch -D &lt;branch-name&gt;</filename>:</emphasis>
1121 Deletes an existing local branch.
1122 You need to be in a local branch other than the one you are deleting
1123 in order to delete <filename>&lt;branch-name&gt;</filename>.</para></listitem>
1124 <listitem><para><emphasis><filename>git pull</filename>:</emphasis> Retrieves information
1125 from an upstream Git
1126 repository and places it in your local Git repository.
1127 You use this command to make sure you are synchronized with the repository
1128 from which you are basing changes (.e.g. the master branch).</para></listitem>
1129 <listitem><para><emphasis><filename>git push</filename>:</emphasis>
1130 Sends all your committed local changes to an upstream Git
1131 repository (e.g. a contribution repository).
1132 The maintainer of the project draws from these repositories
1133 when adding changes to the project’s master repository or
1134 other development branch.
1135 </para></listitem>
1136 <listitem><para><emphasis><filename>git merge</filename>:</emphasis> Combines or adds changes from one
1137 local branch of your repository with another branch.
1138 When you create a local Git repository, the default branch is named "master".
1139 A typical workflow is to create a temporary branch for isolated work, make and commit your
1140 changes, switch to your local master branch, merge the changes from the temporary branch into the
1141 local master branch, and then delete the temporary branch.</para></listitem>
1142 <listitem><para><emphasis><filename>git cherry-pick</filename>:</emphasis> Choose and apply specific
1143 commits from one branch into another branch.
1144 There are times when you might not be able to merge all the changes in one branch with
1145 another but need to pick out certain ones.</para></listitem>
1146 <listitem><para><emphasis><filename>gitk</filename>:</emphasis> Provides a GUI view of the branches
1147 and changes in your local Git repository.
1148 This command is a good way to graphically see where things have diverged in your
1149 local repository.</para></listitem>
1150 <listitem><para><emphasis><filename>git log</filename>:</emphasis> Reports a history of your changes to the
1151 repository.</para></listitem>
1152 <listitem><para><emphasis><filename>git diff</filename>:</emphasis> Displays line-by-line differences
1153 between your local working files and the same files in the upstream Git repository that your
1154 branch currently tracks.</para></listitem>
1155 </itemizedlist>
1156 </para>
1157 </section>
1158</section>
1159
1160<section id='workflows'>
1161 <title>Workflows</title>
1162
1163 <para>
1164 This section provides some overview on workflows using Git.
1165 In particular, the information covers basic practices that describe roles and actions in a
1166 collaborative development environment.
1167 Again, if you are familiar with this type of development environment, you might want to just
1168 skip this section.
1169 </para>
1170
1171 <para>
1172 The Yocto Project files are maintained using Git in a "master" branch whose Git history
1173 tracks every change and whose structure provides branches for all diverging functionality.
1174 Although there is no need to use Git, many open source projects do so.
1175 For the Yocto Project, a key individual called the "maintainer" is responsible for the "master"
1176 branch of a given Git repository.
1177 The "master" branch is the “upstream” repository where the final builds of the project occur.
1178 The maintainer is responsible for accepting changes from other developers and for
1179 organizing the underlying branch structure to reflect release strategies and so forth.
1180 <note>For information on finding out who is responsible for (maintains)
1181 a particular area of code, see the
1182 "<link linkend='how-to-submit-a-change'>How to Submit a Change</link>"
1183 section.
1184 </note>
1185 </para>
1186
1187 <para>
1188 The project also has an upstream contribution Git repository named
1189 <filename>poky-contrib</filename>.
1190 You can see all the branches in this repository using the web interface
1191 of the
1192 <ulink url='&YOCTO_GIT_URL;'>Source Repositories</ulink> organized
1193 within the "Poky Support" area.
1194 These branches temporarily hold changes to the project that have been
1195 submitted or committed by the Yocto Project development team and by
1196 community members who contribute to the project.
1197 The maintainer determines if the changes are qualified to be moved
1198 from the "contrib" branches into the "master" branch of the Git
1199 repository.
1200 </para>
1201
1202 <para>
1203 Developers (including contributing community members) create and maintain cloned repositories
1204 of the upstream "master" branch.
1205 These repositories are local to their development platforms and are used to develop changes.
1206 When a developer is satisfied with a particular feature or change, they "push" the changes
1207 to the appropriate "contrib" repository.
1208 </para>
1209
1210 <para>
1211 Developers are responsible for keeping their local repository up-to-date with "master".
1212 They are also responsible for straightening out any conflicts that might arise within files
1213 that are being worked on simultaneously by more than one person.
1214 All this work is done locally on the developer’s machines before anything is pushed to a
1215 "contrib" area and examined at the maintainer’s level.
1216 </para>
1217
1218 <para>
1219 A somewhat formal method exists by which developers commit changes and push them into the
1220 "contrib" area and subsequently request that the maintainer include them into "master"
1221 This process is called “submitting a patch” or "submitting a change."
1222 For information on submitting patches and changes, see the
1223 "<link linkend='how-to-submit-a-change'>How to Submit a Change</link>" section.
1224 </para>
1225
1226 <para>
1227 To summarize the environment: a single point of entry exists for
1228 changes into the project’s "master" branch of the Git repository,
1229 which is controlled by the project’s maintainer.
1230 And, a set of developers exist who independently develop, test, and
1231 submit changes to "contrib" areas for the maintainer to examine.
1232 The maintainer then chooses which changes are going to become a
1233 permanent part of the project.
1234 </para>
1235
1236 <para>
1237 <imagedata fileref="figures/git-workflow.png" width="6in" depth="3in" align="left" scalefit="1" />
1238 </para>
1239
1240 <para>
1241 While each development environment is unique, there are some best practices or methods
1242 that help development run smoothly.
1243 The following list describes some of these practices.
1244 For more information about Git workflows, see the workflow topics in the
1245 <ulink url='http://book.git-scm.com'>Git Community Book</ulink>.
1246 <itemizedlist>
1247 <listitem><para><emphasis>Make Small Changes:</emphasis> It is best to keep the changes you commit
1248 small as compared to bundling many disparate changes into a single commit.
1249 This practice not only keeps things manageable but also allows the maintainer
1250 to more easily include or refuse changes.</para>
1251 <para>It is also good practice to leave the repository in a state that allows you to
1252 still successfully build your project. In other words, do not commit half of a feature,
1253 then add the other half as a separate, later commit.
1254 Each commit should take you from one buildable project state to another
1255 buildable state.</para></listitem>
1256 <listitem><para><emphasis>Use Branches Liberally:</emphasis> It is very easy to create, use, and
1257 delete local branches in your working Git repository.
1258 You can name these branches anything you like.
1259 It is helpful to give them names associated with the particular feature or change
1260 on which you are working.
1261 Once you are done with a feature or change and have merged it
1262 into your local master branch, simply discard the temporary
1263 branch.</para></listitem>
1264 <listitem><para><emphasis>Merge Changes:</emphasis> The <filename>git merge</filename>
1265 command allows you to take the
1266 changes from one branch and fold them into another branch.
1267 This process is especially helpful when more than a single developer might be working
1268 on different parts of the same feature.
1269 Merging changes also automatically identifies any collisions or "conflicts"
1270 that might happen as a result of the same lines of code being altered by two different
1271 developers.</para></listitem>
1272 <listitem><para><emphasis>Manage Branches:</emphasis> Because branches are easy to use, you should
1273 use a system where branches indicate varying levels of code readiness.
1274 For example, you can have a "work" branch to develop in, a "test" branch where the code or
1275 change is tested, a "stage" branch where changes are ready to be committed, and so forth.
1276 As your project develops, you can merge code across the branches to reflect ever-increasing
1277 stable states of the development.</para></listitem>
1278 <listitem><para><emphasis>Use Push and Pull:</emphasis> The push-pull workflow is based on the
1279 concept of developers "pushing" local commits to a remote repository, which is
1280 usually a contribution repository.
1281 This workflow is also based on developers "pulling" known states of the project down into their
1282 local development repositories.
1283 The workflow easily allows you to pull changes submitted by other developers from the
1284 upstream repository into your work area ensuring that you have the most recent software
1285 on which to develop.
1286 The Yocto Project has two scripts named <filename>create-pull-request</filename> and
1287 <filename>send-pull-request</filename> that ship with the release to facilitate this
1288 workflow.
1289 You can find these scripts in the <filename>scripts</filename>
1290 folder of the
1291 <link linkend='source-directory'>Source Directory</link>.
1292 For information on how to use these scripts, see the
1293 "<link linkend='pushing-a-change-upstream'>Using Scripts to Push a Change Upstream and Request a Pull</link>" section.
1294 </para></listitem>
1295 <listitem><para><emphasis>Patch Workflow:</emphasis> This workflow allows you to notify the
1296 maintainer through an email that you have a change (or patch) you would like considered
1297 for the "master" branch of the Git repository.
1298 To send this type of change, you format the patch and then send the email using the Git commands
1299 <filename>git format-patch</filename> and <filename>git send-email</filename>.
1300 For information on how to use these scripts, see the
1301 "<link linkend='how-to-submit-a-change'>How to Submit a Change</link>"
1302 section.
1303 </para></listitem>
1304 </itemizedlist>
1305 </para>
1306</section>
1307
1308<section id='tracking-bugs'>
1309 <title>Tracking Bugs</title>
1310
1311 <para>
1312 The Yocto Project uses its own implementation of
1313 <ulink url='http://www.bugzilla.org/about/'>Bugzilla</ulink> to track bugs.
1314 Implementations of Bugzilla work well for group development because they track bugs and code
1315 changes, can be used to communicate changes and problems with developers, can be used to
1316 submit and review patches, and can be used to manage quality assurance.
1317 The home page for the Yocto Project implementation of Bugzilla is
1318 <ulink url='&YOCTO_BUGZILLA_URL;'>&YOCTO_BUGZILLA_URL;</ulink>.
1319 </para>
1320
1321 <para>
1322 Sometimes it is helpful to submit, investigate, or track a bug against the Yocto Project itself
1323 such as when discovering an issue with some component of the build system that acts contrary
1324 to the documentation or your expectations.
1325 Following is the general procedure for submitting a new bug using the Yocto Project
1326 Bugzilla.
1327 You can find more information on defect management, bug tracking, and feature request
1328 processes all accomplished through the Yocto Project Bugzilla on the wiki page
1329 <ulink url='&YOCTO_WIKI_URL;/wiki/Bugzilla_Configuration_and_Bug_Tracking'>here</ulink>.
1330 <orderedlist>
1331 <listitem><para>Always use the Yocto Project implementation of Bugzilla to submit
1332 a bug.</para></listitem>
1333 <listitem><para>When submitting a new bug, be sure to choose the appropriate
1334 Classification, Product, and Component for which the issue was found.
1335 Defects for the Yocto Project fall into one of seven classifications:
1336 Yocto Project Components, Infrastructure, Build System &amp; Metadata,
1337 Documentation, QA/Testing, Runtime and Hardware.
1338 Each of these Classifications break down into multiple Products and, in some
1339 cases, multiple Components.</para></listitem>
1340 <listitem><para>Use the bug form to choose the correct Hardware and Architecture
1341 for which the bug applies.</para></listitem>
1342 <listitem><para>Indicate the Yocto Project version you were using when the issue
1343 occurred.</para></listitem>
1344 <listitem><para>Be sure to indicate the Severity of the bug.
1345 Severity communicates how the bug impacted your work.</para></listitem>
1346 <listitem><para>Select the appropriate "Documentation change" item
1347 for the bug.
1348 Fixing a bug may or may not affect the Yocto Project
1349 documentation.</para></listitem>
1350 <listitem><para>Provide a brief summary of the issue.
1351 Try to limit your summary to just a line or two and be sure to capture the
1352 essence of the issue.</para></listitem>
1353 <listitem><para>Provide a detailed description of the issue.
1354 You should provide as much detail as you can about the context, behavior, output,
1355 and so forth that surrounds the issue.
1356 You can even attach supporting files for output from logs by
1357 using the "Add an attachment" button.</para></listitem>
1358 <listitem><para>Be sure to copy the appropriate people in the
1359 "CC List" for the bug.
1360 See the "<link linkend='how-to-submit-a-change'>How to Submit a Change</link>"
1361 section for information about finding out who is responsible
1362 for code.</para></listitem>
1363 <listitem><para>Submit the bug by clicking the "Submit Bug" button.</para></listitem>
1364 </orderedlist>
1365 </para>
1366</section>
1367
1368<section id='how-to-submit-a-change'>
1369 <title>How to Submit a Change</title>
1370
1371 <para>
1372 Contributions to the Yocto Project and OpenEmbedded are very welcome.
1373 Because the system is extremely configurable and flexible, we recognize that developers
1374 will want to extend, configure or optimize it for their specific uses.
1375 You should send patches to the appropriate mailing list so that they
1376 can be reviewed and merged by the appropriate maintainer.
1377 </para>
1378
1379 <para>
1380 Before submitting any change, be sure to find out who you should be
1381 notifying.
1382 Several methods exist through which you find out who you should be copying
1383 or notifying:
1384 <itemizedlist>
1385 <listitem><para><emphasis>Maintenance File:</emphasis>
1386 Examine the <filename>maintainers.inc</filename> file, which is
1387 located in the
1388 <link linkend='source-directory'>Source Directory</link>
1389 at <filename>meta-yocto/conf/distro/include</filename>, to
1390 see who is responsible for code.
1391 </para></listitem>
1392 <listitem><para><emphasis>Board Support Package (BSP) README Files:</emphasis>
1393 For BSP maintainers of supported BSPs, you can examine
1394 individual BSP <filename>README</filename> files.
1395 In addition, some layers (such as the <filename>meta-intel</filename> layer),
1396 include a <filename>MAINTAINERS</filename> file which contains
1397 a list of all supported BSP maintainers for that layer.
1398 </para></listitem>
1399 <listitem><para><emphasis>Search by File:</emphasis>
1400 Using <link linkend='git'>Git</link>, you can enter the
1401 following command to bring up a short list of all commits
1402 against a specific file:
1403 <literallayout class='monospaced'>
1404 git shortlog -- <replaceable>filename</replaceable>
1405 </literallayout>
1406 Just provide the name of the file for which you are interested.
1407 The information returned is not ordered by history but does
1408 include a list of all committers grouped by name.
1409 From the list, you can see who is responsible for the bulk of
1410 the changes against the file.
1411 </para></listitem>
1412 </itemizedlist>
1413 </para>
1414
1415 <para>
1416 For a list of the Yocto Project and related mailing lists, see the
1417 "<ulink url='&YOCTO_DOCS_REF_URL;#resources-mailinglist'>Mailing lists</ulink>" section in
1418 the Yocto Project Reference Manual.
1419 </para>
1420
1421 <para>
1422 Here is some guidance on which mailing list to use for what type of change:
1423 <itemizedlist>
1424 <listitem><para>For changes to the core
1425 <link linkend='metadata'>Metadata</link>, send your patch to the
1426 <ulink url='&OE_LISTS_URL;/listinfo/openembedded-core'>openembedded-core</ulink> mailing list.
1427 For example, a change to anything under the <filename>meta</filename> or
1428 <filename>scripts</filename> directories
1429 should be sent to this mailing list.</para></listitem>
1430 <listitem><para>For changes to BitBake (anything under the <filename>bitbake</filename>
1431 directory), send your patch to the
1432 <ulink url='&OE_LISTS_URL;/listinfo/bitbake-devel'>bitbake-devel</ulink> mailing list.</para></listitem>
1433 <listitem><para>For changes to <filename>meta-yocto</filename>, send your patch to the
1434 <ulink url='&YOCTO_LISTS_URL;/listinfo/poky'>poky</ulink> mailing list.</para></listitem>
1435 <listitem><para>For changes to other layers hosted on
1436 <filename>yoctoproject.org</filename> (unless the
1437 layer's documentation specifies otherwise), tools, and Yocto Project
1438 documentation, use the
1439 <ulink url='&YOCTO_LISTS_URL;/listinfo/yocto'>yocto</ulink> mailing list.</para></listitem>
1440 <listitem><para>For additional recipes that do not fit into the core Metadata,
1441 you should determine which layer the recipe should go into and submit the
1442 change in the manner recommended by the documentation (e.g. README) supplied
1443 with the layer. If in doubt, please ask on the
1444 <ulink url='&YOCTO_LISTS_URL;/listinfo/yocto'>yocto</ulink> or
1445 <ulink url='&OE_LISTS_URL;/listinfo/openembedded-devel'>openembedded-devel</ulink>
1446 mailing lists.</para></listitem>
1447 </itemizedlist>
1448 </para>
1449
1450 <para>
1451 When you send a patch, be sure to include a "Signed-off-by:"
1452 line in the same style as required by the Linux kernel.
1453 Adding this line signifies that you, the submitter, have agreed to the Developer's Certificate of Origin 1.1
1454 as follows:
1455 <literallayout class='monospaced'>
1456 Developer's Certificate of Origin 1.1
1457
1458 By making a contribution to this project, I certify that:
1459
1460 (a) The contribution was created in whole or in part by me and I
1461 have the right to submit it under the open source license
1462 indicated in the file; or
1463
1464 (b) The contribution is based upon previous work that, to the best
1465 of my knowledge, is covered under an appropriate open source
1466 license and I have the right under that license to submit that
1467 work with modifications, whether created in whole or in part
1468 by me, under the same open source license (unless I am
1469 permitted to submit under a different license), as indicated
1470 in the file; or
1471
1472 (c) The contribution was provided directly to me by some other
1473 person who certified (a), (b) or (c) and I have not modified
1474 it.
1475
1476 (d) I understand and agree that this project and the contribution
1477 are public and that a record of the contribution (including all
1478 personal information I submit with it, including my sign-off) is
1479 maintained indefinitely and may be redistributed consistent with
1480 this project or the open source license(s) involved.
1481 </literallayout>
1482 </para>
1483
1484 <para>
1485 In a collaborative environment, it is necessary to have some sort of standard
1486 or method through which you submit changes.
1487 Otherwise, things could get quite chaotic.
1488 One general practice to follow is to make small, controlled changes.
1489 Keeping changes small and isolated aids review, makes merging/rebasing easier
1490 and keeps the change history clean when anyone needs to refer to it in future.
1491 </para>
1492
1493 <para>
1494 When you make a commit, you must follow certain standards established by the
1495 OpenEmbedded and Yocto Project development teams.
1496 For each commit, you must provide a single-line summary of the change and you
1497 should almost always provide a more detailed description of what you did (i.e.
1498 the body of the commit message).
1499 The only exceptions for not providing a detailed description would be if your
1500 change is a simple, self-explanatory change that needs no further description
1501 beyond the summary.
1502 Here are the guidelines for composing a commit message:
1503 <itemizedlist>
1504 <listitem><para>Provide a single-line, short summary of the change.
1505 This summary is typically viewable in the "shortlist" of changes.
1506 Thus, providing something short and descriptive that gives the reader
1507 a summary of the change is useful when viewing a list of many commits.
1508 This short description should be prefixed by the recipe name (if changing a recipe), or
1509 else the short form path to the file being changed.
1510 </para></listitem>
1511 <listitem><para>For the body of the commit message, provide detailed information
1512 that describes what you changed, why you made the change, and the approach
1513 you used. It may also be helpful if you mention how you tested the change.
1514 Provide as much detail as you can in the body of the commit message.
1515 </para></listitem>
1516 <listitem><para>
1517 If the change addresses a specific bug or issue that is
1518 associated with a bug-tracking ID, include a reference to that
1519 ID in your detailed description.
1520 For example, the Yocto Project uses a specific convention for
1521 bug references - any commit that addresses a specific bug should
1522 use the following form for the detailed description:
1523 <literallayout class='monospaced'>
1524 Fixes [YOCTO #<replaceable>bug-id</replaceable>]
1525
1526 <replaceable>detailed description of change</replaceable>
1527 </literallayout></para></listitem>
1528 Where <replaceable>bug-id</replaceable> is replaced with the
1529 specific bug ID from the Yocto Project Bugzilla instance.
1530 </itemizedlist>
1531 </para>
1532
1533 <para>
1534 You can find more guidance on creating well-formed commit messages at this OpenEmbedded
1535 wiki page:
1536 <ulink url='&OE_HOME_URL;/wiki/Commit_Patch_Message_Guidelines'></ulink>.
1537 </para>
1538
1539 <para>
1540 The next two sections describe general instructions for both pushing
1541 changes upstream and for submitting changes as patches.
1542 </para>
1543
1544 <section id='pushing-a-change-upstream'>
1545 <title>Using Scripts to Push a Change Upstream and Request a Pull</title>
1546
1547 <para>
1548 The basic flow for pushing a change to an upstream "contrib" Git repository is as follows:
1549 <itemizedlist>
1550 <listitem><para>Make your changes in your local Git repository.</para></listitem>
1551 <listitem><para>Stage your changes by using the <filename>git add</filename>
1552 command on each file you changed.</para></listitem>
1553 <listitem><para>
1554 Commit the change by using the
1555 <filename>git commit</filename> command.
1556 Be sure to provide a commit message that follows the
1557 project’s commit message standards as described earlier.
1558 </para></listitem>
1559 <listitem><para>
1560 Push the change to the upstream "contrib" repository by
1561 using the <filename>git push</filename> command.
1562 </para></listitem>
1563 <listitem><para>Notify the maintainer that you have pushed a change by making a pull
1564 request.
1565 The Yocto Project provides two scripts that conveniently let you generate and send
1566 pull requests to the Yocto Project.
1567 These scripts are <filename>create-pull-request</filename> and
1568 <filename>send-pull-request</filename>.
1569 You can find these scripts in the <filename>scripts</filename> directory
1570 within the <link linkend='source-directory'>Source Directory</link>.</para>
1571 <para>Using these scripts correctly formats the requests without introducing any
1572 whitespace or HTML formatting.
1573 The maintainer that receives your patches needs to be able to save and apply them
1574 directly from your emails.
1575 Using these scripts is the preferred method for sending patches.</para>
1576 <para>For help on using these scripts, simply provide the
1577 <filename>-h</filename> argument as follows:
1578 <literallayout class='monospaced'>
1579 $ poky/scripts/create-pull-request -h
1580 $ poky/scripts/send-pull-request -h
1581 </literallayout></para></listitem>
1582 </itemizedlist>
1583 </para>
1584
1585 <para>
1586 You can find general Git information on how to push a change upstream in the
1587 <ulink url='http://book.git-scm.com/3_distributed_workflows.html'>Git Community Book</ulink>.
1588 </para>
1589 </section>
1590
1591 <section id='submitting-a-patch'>
1592 <title>Using Email to Submit a Patch</title>
1593
1594 <para>
1595 You can submit patches without using the <filename>create-pull-request</filename> and
1596 <filename>send-pull-request</filename> scripts described in the previous section.
1597 However, keep in mind, the preferred method is to use the scripts.
1598 </para>
1599
1600 <para>
1601 Depending on the components changed, you need to submit the email to a specific
1602 mailing list.
1603 For some guidance on which mailing list to use, see the list in the
1604 "<link linkend='how-to-submit-a-change'>How to Submit a Change</link>"
1605 section.
1606 For a description of the available mailing lists, see the
1607 "<ulink url='&YOCTO_DOCS_REF_URL;#resources-mailinglist'>Mailing Lists</ulink>"
1608 section in the Yocto Project Reference Manual.
1609 </para>
1610
1611 <para>
1612 Here is the general procedure on how to submit a patch through email without using the
1613 scripts:
1614 <itemizedlist>
1615 <listitem><para>Make your changes in your local Git repository.</para></listitem>
1616 <listitem><para>Stage your changes by using the <filename>git add</filename>
1617 command on each file you changed.</para></listitem>
1618 <listitem><para>Commit the change by using the
1619 <filename>git commit --signoff</filename> command.
1620 Using the <filename>--signoff</filename> option identifies you as the person
1621 making the change and also satisfies the Developer's Certificate of
1622 Origin (DCO) shown earlier.</para>
1623 <para>When you form a commit, you must follow certain standards established by the
1624 Yocto Project development team.
1625 See the earlier section
1626 "<link linkend='how-to-submit-a-change'>How to Submit a Change</link>"
1627 for Yocto Project commit message standards.</para></listitem>
1628 <listitem><para>Format the commit into an email message.
1629 To format commits, use the <filename>git format-patch</filename> command.
1630 When you provide the command, you must include a revision list or a number of patches
1631 as part of the command.
1632 For example, either of these two commands takes your most
1633 recent single commit and formats it as an email message in
1634 the current directory:
1635 <literallayout class='monospaced'>
1636 $ git format-patch -1
1637 </literallayout>
1638 or
1639 <literallayout class='monospaced'>
1640 $ git format-patch HEAD~
1641 </literallayout></para>
1642 <para>After the command is run, the current directory contains a
1643 numbered <filename>.patch</filename> file for the commit.</para>
1644 <para>If you provide several commits as part of the command,
1645 the <filename>git format-patch</filename> command produces a
1646 series of numbered files in the current directory – one for each commit.
1647 If you have more than one patch, you should also use the
1648 <filename>--cover</filename> option with the command, which generates a
1649 cover letter as the first "patch" in the series.
1650 You can then edit the cover letter to provide a description for
1651 the series of patches.
1652 For information on the <filename>git format-patch</filename> command,
1653 see <filename>GIT_FORMAT_PATCH(1)</filename> displayed using the
1654 <filename>man git-format-patch</filename> command.</para>
1655 <note>If you are or will be a frequent contributor to the Yocto Project
1656 or to OpenEmbedded, you might consider requesting a contrib area and the
1657 necessary associated rights.</note></listitem>
1658 <listitem><para>Import the files into your mail client by using the
1659 <filename>git send-email</filename> command.
1660 <note>In order to use <filename>git send-email</filename>, you must have the
1661 the proper Git packages installed.
1662 For Ubuntu, Debian, and Fedora the package is <filename>git-email</filename>.</note></para>
1663 <para>The <filename>git send-email</filename> command sends email by using a local
1664 or remote Mail Transport Agent (MTA) such as
1665 <filename>msmtp</filename>, <filename>sendmail</filename>, or through a direct
1666 <filename>smtp</filename> configuration in your Git <filename>config</filename>
1667 file.
1668 If you are submitting patches through email only, it is very important
1669 that you submit them without any whitespace or HTML formatting that
1670 either you or your mailer introduces.
1671 The maintainer that receives your patches needs to be able to save and
1672 apply them directly from your emails.
1673 A good way to verify that what you are sending will be applicable by the
1674 maintainer is to do a dry run and send them to yourself and then
1675 save and apply them as the maintainer would.</para>
1676 <para>The <filename>git send-email</filename> command is the preferred method
1677 for sending your patches since there is no risk of compromising whitespace
1678 in the body of the message, which can occur when you use your own mail client.
1679 The command also has several options that let you
1680 specify recipients and perform further editing of the email message.
1681 For information on how to use the <filename>git send-email</filename> command,
1682 see <filename>GIT-SEND-EMAIL(1)</filename> displayed using
1683 the <filename>man git-send-email</filename> command.
1684 </para></listitem>
1685 </itemizedlist>
1686 </para>
1687 </section>
1688</section>
1689</chapter>
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