1.. _pullrequests:
2
3Creating Pull Requests
4======================
5
6This chapter describes how maintainers can create and submit pull requests
7to other maintainers. This is useful for transferring changes from one
8maintainers tree to another maintainers tree.
9
10This document was written by Tobin C. Harding (who at that time, was not an
11experienced maintainer) primarily from comments made by Greg Kroah-Hartman
12and Linus Torvalds on LKML. Suggestions and fixes by Jonathan Corbet and
13Mauro Carvalho Chehab.  Misrepresentation was unintentional but inevitable,
14please direct abuse to Tobin C. Harding <me@tobin.cc>.
15
16Original email thread::
17
18	http://lkml.kernel.org/r/20171114110500.GA21175@kroah.com
19
20
21Create Branch
22-------------
23
24To start with you will need to have all the changes you wish to include in
25the pull request on a separate branch. Typically you will base this branch
26off of a branch in the developers tree whom you intend to send the pull
27request to.
28
29In order to create the pull request you must first tag the branch that you
30have just created. It is recommended that you choose a meaningful tag name,
31in a way that you and others can understand, even after some time.  A good
32practice is to include in the name an indicator of the sybsystem of origin
33and the target kernel version.
34
35Greg offers the following. A pull request with miscellaneous stuff for
36drivers/char, to be applied at the Kernel version 4.15-rc1 could be named
37as ``char-misc-4.15-rc1``. If such tag would be produced from a branch
38named ``char-misc-next``, you would be using the following command::
39
40        git tag -s char-misc-4.15-rc1 char-misc-next
41
42that will create a signed tag called ``char-misc-4.15-rc1`` based on the
43last commit in the ``char-misc-next`` branch, and sign it with your gpg key
44(see :ref:`Documentation/maintainer/configure-git.rst <configuregit>`).
45
46Linus will only accept pull requests based on a signed tag. Other
47maintainers may differ.
48
49When you run the above command ``git`` will drop you into an editor and ask
50you to describe the tag.  In this case, you are describing a pull request,
51so outline what is contained here, why it should be merged, and what, if
52any, testing has been done.  All of this information will end up in the tag
53itself, and then in the merge commit that the maintainer makes if/when they
54merge the pull request. So write it up well, as it will be in the kernel
55tree for forever.
56
57As said by Linus::
58
59	Anyway, at least to me, the important part is the *message*. I want
60	to understand what I'm pulling, and why I should pull it. I also
61	want to use that message as the message for the merge, so it should
62	not just make sense to me, but make sense as a historical record
63	too.
64
65	Note that if there is something odd about the pull request, that
66	should very much be in the explanation. If you're touching files
67	that you don't maintain, explain _why_. I will see it in the
68	diffstat anyway, and if you didn't mention it, I'll just be extra
69	suspicious.  And when you send me new stuff after the merge window
70	(or even bug-fixes, but ones that look scary), explain not just
71	what they do and why they do it, but explain the _timing_. What
72	happened that this didn't go through the merge window..
73
74	I will take both what you write in the email pull request _and_ in
75	the signed tag, so depending on your workflow, you can either
76	describe your work in the signed tag (which will also automatically
77	make it into the pull request email), or you can make the signed
78	tag just a placeholder with nothing interesting in it, and describe
79	the work later when you actually send me the pull request.
80
81	And yes, I will edit the message. Partly because I tend to do just
82	trivial formatting (the whole indentation and quoting etc), but
83	partly because part of the message may make sense for me at pull
84	time (describing the conflicts and your personal issues for sending
85	it right now), but may not make sense in the context of a merge
86	commit message, so I will try to make it all make sense. I will
87	also fix any speeling mistaeks and bad grammar I notice,
88	particularly for non-native speakers (but also for native ones
89	;^). But I may miss some, or even add some.
90
91			Linus
92
93Greg gives, as an example pull request::
94
95	Char/Misc patches for 4.15-rc1
96
97	Here is the big char/misc patch set for the 4.15-rc1 merge window.
98	Contained in here is the normal set of new functions added to all
99	of these crazy drivers, as well as the following brand new
100	subsystems:
101		- time_travel_controller: Finally a set of drivers for the
102		  latest time travel bus architecture that provides i/o to
103		  the CPU before it asked for it, allowing uninterrupted
104		  processing
105		- relativity_shifters: due to the affect that the
106		  time_travel_controllers have on the overall system, there
107		  was a need for a new set of relativity shifter drivers to
108		  accommodate the newly formed black holes that would
109		  threaten to suck CPUs into them.  This subsystem handles
110		  this in a way to successfully neutralize the problems.
111		  There is a Kconfig option to force these to be enabled
112		  when needed, so problems should not occur.
113
114	All of these patches have been successfully tested in the latest
115	linux-next releases, and the original problems that it found have
116	all been resolved (apologies to anyone living near Canberra for the
117	lack of the Kconfig options in the earlier versions of the
118	linux-next tree creations.)
119
120	Signed-off-by: Your-name-here <your_email@domain>
121
122
123The tag message format is just like a git commit id.  One line at the top
124for a "summary subject" and be sure to sign-off at the bottom.
125
126Now that you have a local signed tag, you need to push it up to where it
127can be retrieved::
128
129	git push origin char-misc-4.15-rc1
130
131
132Create Pull Request
133-------------------
134
135The last thing to do is create the pull request message.  ``git`` handily
136will do this for you with the ``git request-pull`` command, but it needs a
137bit of help determining what you want to pull, and on what to base the pull
138against (to show the correct changes to be pulled and the diffstat). The
139following command(s) will generate a pull request::
140
141	git request-pull master git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git/ char-misc-4.15-rc1
142
143Quoting Greg::
144
145	This is asking git to compare the difference from the
146	'char-misc-4.15-rc1' tag location, to the head of the 'master'
147	branch (which in my case points to the last location in Linus's
148	tree that I diverged from, usually a -rc release) and to use the
149	git:// protocol to pull from.  If you wish to use https://, that
150	can be used here instead as well (but note that some people behind
151	firewalls will have problems with https git pulls).
152
153	If the char-misc-4.15-rc1 tag is not present in the repo that I am
154	asking to be pulled from, git will complain saying it is not there,
155	a handy way to remember to actually push it to a public location.
156
157	The output of 'git request-pull' will contain the location of the
158	git tree and specific tag to pull from, and the full text
159	description of that tag (which is why you need to provide good
160	information in that tag).  It will also create a diffstat of the
161	pull request, and a shortlog of the individual commits that the
162	pull request will provide.
163
164Linus responded that he tends to prefer the ``git://`` protocol. Other
165maintainers may have different preferences. Also, note that if you are
166creating pull requests without a signed tag then ``https://`` may be a
167better choice. Please see the original thread for the full discussion.
168
169
170Submit Pull Request
171-------------------
172
173A pull request is submitted in the same way as an ordinary patch. Send as
174inline email to the maintainer and CC LKML and any sub-system specific
175lists if required. Pull requests to Linus typically have a subject line
176something like::
177
178	[GIT PULL] <subsystem> changes for v4.15-rc1
179