Message-ID: <20171114164816.5bf8f87f@lwn.net>
Date:   Tue, 14 Nov 2017 16:48:16 -0700
From:   Jonathan Corbet <corbet@....net>
To:     "Tobin C. Harding" <me@...in.cc>
Cc:     linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH] docs: add submitting-pull-requests.rst

On Wed, 15 Nov 2017 09:54:21 +1100
"Tobin C. Harding" <me@...in.cc> wrote:

> There is currently no documentation on how to create a pull request for
> Linus.
> 
>     Anyway, this actually came up at the kernel summit / maintainer
>     meeting a few weeks ago, in that "how do I make a good pull request
>     to Linus" is something we need to document.
> 
>     Here's what I do, and it seems to work well, so maybe we should turn
>     it into the start of the documentation for how to do it.
> 
> Create document from email thread on LKML (referenced in document).
> 
> Signed-off-by: Tobin C. Harding <me@...in.cc>
> ---
> 
> Is it rude to send this during the merge window? Can resend after it closes if
> it makes life easier.

I can handle patches during the merge window.  That said, while I welcome
this effort and think it's a good start, there's a few things I'll
quibble about:

 - Much of this was actually written by Greg, I believe, and some by Linus.
   That deserves credit in the changelog, if nowhere else.

 - Putting it in Documentation/process as RST is good.  But it should be
   added to index.rst and made part of the docs build.  I suspect you
   haven't run it through sphinx at all yet, right?  Some things are
   unlikely to format the way you think they might.

Finally, I see this as being the first installment in what, I hope, will
someday be a nice "how to be a kernel maintainer" manual.  I wouldn't
insist on it before taking a patch like this, but if you could see
through to organizing it as a chapter in a bigger sub-book, that would be
great.

Finally finally... Dan Williams [CC'd] has plans for doing some
maintainer-level documentation.  He may have thoughts on how this fits
into what he's scheming, and I'd suggest copying him on the next
iteration.

Finally finally finally...some specific comments on the text.  Some of
them might be read to suggest a major expansion of the work you've done;
please see that as me saying "that would be nice".  Doing all of this is
not a precondition to getting this document added!

> +Submitting Pull Requests to Linus: a guide for maintainers
> +==========================================================
> +
> +This document is aimed at kernel maintainers.  It describes a method for creating
> +a pull request to be sent to Linus.

Limiting text widths to, say, 75 columns when possible is preferable.  Word
has it some maintainers are still reading the docs on their adm3a
terminals.

Most maintainers push directly to Linus, so that's an obvious best focus,
but pull requests happen at other levels too.  One would hope that this
information would be applicable at all levels, so it might be nice to
describe it as such.

> +Configure Git
> +-------------

"Configure Git to use your private key"

We are, of course, missing the whole discussion on why one would want a
keypair, how to create it, how to get it into the web of trust, etc.  All
fodder for a separate chapter in our shiny new maintainer book :)  But it
is worth saying at least that this is about making Git use your key so you
can sign tags for pull requests.

> +Since you _usually_ would use the same key for the same project, just set it
> +once with

If you end a line like that with "::", the following indented section will
be formatted as code by sphinx.  That's almost always what you want.

> +	git config user.signingkey "keyname"
> +
> +and if you use the same key for everything, just add "--global".
> +
> +Or just edit your .git/config or ~/.gitconfig file by hand, it's designed to be
> +human-readable and writable, and not some garbage like XML:
> +
> +	[torvalds@i7 ~]$ head -4 .gitconfig
> +	[user]
> +		name = Linus Torvalds
> +		email = torvalds@...ux-foundation.org
> +		signingkey = torvalds@...ux-foundation.org
> +
> +You may need to tell git to use gpg2
> +
> +	[gpg]
> +		program = /path/to/gpg2
> +
> +You may also like to tell gpg which tty to use (add to shell rc file)
> +
> +	export GPG_TTY=$(tty)
> +
> +
> +Branch, Tag, Push
> +-----------------
> +
> +Next, put your changes on a branch, hopefully one named in a semi-useful way (I
> +use 'char-misc-next' for my char/misc driver patches to be merged into
> +linux-next).  That is the branch you wish to tag and have Linus pull from.

Management of patches and branches would, of course, make for another nice
chapter.

> +Name the tag with something useful that you can understand if you run across it
> +in a few weeks, and something that will be "unique".  Continuing the example of

Greg likes to put quotes in weird places, but we don't need to preserve
that :)  Git will force the tag to be "unique", so we can just say unique. 

> +the char-misc tree, for the patches to be sent to Linus for the 4.15-rc1 merge
> +window, I would name the tag 'char-misc-4.15-rc1':
> +
> +	git tag -s char-misc-4.15-rc1 char-misc-next
> +
> +that will create a signed tag called 'char-misc-4.15-rc1' based on the last
> +commit in the char-misc-next branch, and sign it with your gpg key (configured
> +above).
> +
> +When you run the above command, git will drop you into an editor and ask you to
> +describe the tag.  In this case, you are describing a pull request, so outline
> +what is contained here, why it should be merged, and what, if any, testing has
> +happened to it.  All of this information will end up in the tag itself, and then
> +in the merge commit that Linus makes, so write it up well, as it will be in the
> +kernel tree for forever.

s/for//

Sphinx will format the following indented text differently, which may not
be what you want.  I think you should really introduce it with "Linus said
this:" perhaps with a link to the list archive.

> +	Anyway, at least to me, the important part is the *message*. I want to
> +	understand what I'm pulling, and why I should pull it. I also want to
> +	use that message as the message for the merge, so it should not just
> +	make sense to me, but make sense as a historical record too.
> +
> +	Note that if there is something odd about the pull request, that
> +	should very much be in the explanation. If you're touching files that
> +	you don't maintain, explain _why_. I will see it in the diffstat
> +	anyway, and if you didn't mention it, I'll just be extra suspicious.
> +	And when you send me new stuff after the merge window (or even
> +	bug-fixes, but ones that look scary), explain not just what they do
> +	and why they do it, but explain the _timing_. What happened that this
> +	didn't go through the merge window..
> +
> +	I will take both what you write in the email pull request _and_ in the
> +	signed tag, so depending on your workflow, you can either describe
> +	your work in the signed tag (which will also automatically make it
> +	into the pull request email), or you can make the signed tag just a
> +	placeholder with nothing interesting in it, and describe the work
> +	later when you actually send me the pull request.
> +
> +	And yes, I will edit the message. Partly because I tend to do just
> +	trivial formatting (the whole indentation and quoting etc), but partly
> +	because part of the message may make sense for me at pull time
> +	(describing the conflicts and your personal issues for sending it
> +	right now), but may not make sense in the context of a merge commit
> +	message, so I will try to make it all make sense. I will also fix any
> +	speeling mistaeks and bad grammar I notice, particularly for
> +	non-native speakers (but also for native ones ;^). But I may miss
> +	some, or even add some.
> +
> +			Linus
> +
> +An example pull request of mine might look like:

Here's a change of voice back to Greg.  Be careful about appearing to put
one person's words into another's mouth.

Here you definitely want the :: treatment, or sphinx will whine about the
strange (to it) indents.

> +	Char/Misc patches for 4.15-rc1
> +
> +	Here is the big char/misc patch set for the 4.15-rc1 merge
> +	window.  Contained in here is the normal set of new functions
> +	added to all of these crazy drivers, as well as the following
> +	brand new subsystems:
> +		- time_travel_controller: Finally a set of drivers for
> +		  the latest time travel bus architecture that provides
> +		  i/o to the CPU before it asked for it, allowing
> +		  uninterrupted processing
> +		- relativity_shifters: due to the affect that the
> +		  time_travel_controllers have on the overall system,
> +		  there was a need for a new set of relativity shifter
> +		  drivers to accommodate the newly formed black holes
> +		  that would threaten to suck CPUs into them.  This
> +		  subsystem handles this in a way to successfully
> +		  neutralize the problems.  There is a Kconfig option to
> +		  force these to be enabled when needed, so problems
> +		  should not occur.
> +
> +	All of these patches have been successfully tested in the latest
> +	linux-next releases, and the original problems that it found
> +	have all been resolved (apologies to anyone living near Canberra
> +	for the lack of the Kconfig options in the earlier versions of
> +	the linux-next tree creations.)
> +
> +	Signed-off-by: Your-name-here <your_email@...ain>
> +
> +
> +The tag message format is just like a git commit id.  One line at the top for a
> +"summary subject" and be sure to sign-off at the bottom.

FWIW, I've never formatted tag messages that way, and I'm not sure how many
others do.  But perhaps we should all be doing it?

> +Now that you have a local signed tag, you need to push it up to where it can be
> +retrieved by Linus:
> +
> +	git push origin char-misc-4.15-rc1
> +
> +pushes the char-misc-4.15-rc1 tag to where the 'origin' repo is located.
> +
> +
> +Create Pull Request
> +-------------------
> +
> +The last thing to do is create the pull request message.  Git handily will do
> +this for you with the 'git request-pull' command, but it needs a bit of help
> +determining what you want to pull, and what to base the pull against (to show
> +the correct changes to be pulled and the diffstat.)
> +
> +The following command(s) will generate a pull request:
> +
> +	$TREE=git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git/

I don't believe that $ is correct

> +	git request-pull master $TREE char-misc-4.15-rc1
> +
> +This is asking git to compare the difference from the 'char-misc-4.15-rc1' tag
> +location, to the head of the 'master' branch (which in my case points to the
> +last location in Linus's tree that I diverged from, usually a -rc release).
> +
> +Note: please use the git protocol (for justification from Linus see referenced
> +email thread).

We need a reference to that thread.

> +If the char-misc-4.15-rc1 tag is not present in the repo that I am asking to be
> +pulled from, git will complain saying it is not there, a handy way to remember
> +to actually push it to a public location.
> +
> +The output of 'git request-pull' will contain the location of the git tree and
> +specific tag to pull from, and the full text description of that tag (which is
> +why you need to provide good information in that tag.)  It will also create a
> +diffstat of the pull request, and a shortlog of the individual commits that the
> +pull request will provide.
> +
> +
> +References
> +----------
> +
> +The thread that this document is based on:
> +
> +	https://lkml.org/lkml/2017/11/14/184

Ah, there's that reference.  I think it should be at the top before you
first start quoting from it.

I think there's something missing here: what do you do with that output
from 'git request-pull'?  There should be a little section on emailing it
to the relevant upstream maintainer and how to decide where to copy the
request to.  Pull requests should always be copied to a public list so that
others know that the request has been made.  Some guidance on subject-line
formatting would be good; as I recall, Linus filters mail that says "git"
or "pull" specially.  I might also add something about how to know when the
pull has happened (sign up to the commits list if nothing else).

Thanks for doing this,

jon

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