I started reading over the SubmittingPatches document for Git, primarily because
I wanted to have a document similar to it for OfflineIMAP to make sure people
understand what they are doing when they write Signed-off-by line.
But the patch submission requirements are a lot more relaxed here on the
technical/contents front, because the OfflineIMAP is a lot smaller ;-). So here
is only the relevant bits.
Decide what branch to base your work on
In general, always base your work on the oldest branch that your
change is relevant to.
- A bugfix should be based on ‘maint’ in general. If the bug is not
present in ‘maint’, base it on ‘master’. For a bug that’s not yet
in ‘master’, find the topic that introduces the regression, and
base your work on the tip of the topic.
- A new feature should be based on ‘master’ in general. If the new
feature depends on a topic that is in ‘pu’, but not in ‘master’,
base your work on the tip of that topic.
- Corrections and enhancements to a topic not yet in ‘master’ should
be based on the tip of that topic. If the topic has not been merged
to ‘next’, it’s alright to add a note to squash minor corrections
into the series.
- In the exceptional case that a new feature depends on several topics
not in ‘master’, start working on ‘next’ or ‘pu’ privately and send
out patches for discussion. Before the final merge, you may have to
wait until some of the dependent topics graduate to ‘master’, and
rebase your work.
To find the tip of a topic branch, run git log --first-parent
master..pu and look for the merge commit. The second parent of this
commit is the tip of the topic branch.
Make separate commits for logically separate changes
Unless your patch is really trivial, you should not be sending your
changes in a single patch. Instead, always make a commit with
complete commit message and generate a series of small patches from
your repository.
Describe the technical detail of the change(s).
If your description starts to get too long, that’s a sign that you
probably need to split up your commit to finer grained pieces.
That being said, patches which plainly describe the things that
help reviewers check the patch, and future maintainers understand
the code, are the most beautiful patches. Descriptions that summarise
the point in the subject well, and describe the motivation for the
change, the approach taken by the change, and if relevant how this
differs substantially from the prior version, can be found on Usenet
archives back into the late 80’s. Consider it like good Netiquette,
but for code.
Sending your patches
People on the mailing list need to be able to read and
comment on the changes you are submitting. It is important for
a developer to be able to “quote” your changes, using standard
e-mail tools, so that they may comment on specific portions of
your code. For this reason, all patches should be submitted
“inline”. WARNING: Be wary of your MUAs word-wrap
corrupting your patch. Do not cut-n-paste your patch; you can
lose tabs that way if you are not careful.
It is a common convention to prefix your subject line with
[PATCH]. This lets people easily distinguish patches from other
e-mail discussions. Use of additional markers after PATCH and
the closing bracket to mark the nature of the patch is also
encouraged. E.g. [PATCH/RFC] is often used when the patch is
not ready to be applied but it is for discussion, [PATCH v2],
[PATCH v3] etc. are often seen when you are sending an update to
what you have previously sent.
git format-patch command follows the best current practice to
format the body of an e-mail message. At the beginning of the
patch should come your commit message, ending with the
Signed-off-by: lines, and a line that consists of three dashes,
followed by the diffstat information and the patch itself. If
you are forwarding a patch from somebody else, optionally, at
the beginning of the e-mail message just before the commit
message starts, you can put a “From: ” line to name that person.
You often want to add additional explanation about the patch,
other than the commit message itself. Place such “cover letter”
material between the three dash lines and the diffstat.
Do not attach the patch as a MIME attachment, compressed or not.
Do not let your e-mail client send quoted-printable. Do not let
your e-mail client send format=flowed which would destroy
whitespaces in your patches. Many
popular e-mail applications will not always transmit a MIME
attachment as plain text, making it impossible to comment on
your code. A MIME attachment also takes a bit more time to
process. This does not decrease the likelihood of your
MIME-attached change being accepted, but it makes it more likely
that it will be postponed.
Exception: If your mailer is mangling patches then someone may ask
you to re-send them using MIME, that is OK.
Do not PGP sign your patch, at least for now. Most likely, your
maintainer or other people on the list would not have your PGP
key and would not bother obtaining it anyway. Your patch is not
judged by who you are; a good patch from an unknown origin has a
far better chance of being accepted than a patch from a known,
respected origin that is done poorly or does incorrect things.
If you really really really really want to do a PGP signed
patch, format it as “multipart/signed”, not a text/plain message
that starts with ‘—–BEGIN PGP SIGNED MESSAGE—–’. That is
not a text/plain, it’s something else.
Unless your patch is a very trivial and an obviously correct one,
first send it with “To:” set to the mailing list, with “cc:” listing
people who are involved in the area you are touching (the output from
“git blame $path” and “git shortlog –no-merges $path” would help to
identify them), to solicit comments and reviews. After the list
reached a consensus that it is a good idea to apply the patch, re-send
it with “To:” set to the maintainer and optionally “cc:” the list for
inclusion. Do not forget to add trailers such as “Acked-by:”,
“Reviewed-by:” and “Tested-by:” after your “Signed-off-by:” line as
necessary.
Sign your work
To improve tracking of who did what, we’ve borrowed the
“sign-off” procedure from the Linux kernel project on patches
that are being emailed around. Although OfflineIMAP is a lot
smaller project it is a good discipline to follow it.
The sign-off is a simple line at the end of the explanation for
the patch, which certifies that you wrote it or otherwise have
the right to pass it on as a open-source patch. The rules are
pretty simple: if you can certify the below:
Developer’s Certificate of Origin 1.1
By making a contribution to this project, I certify that:
The contribution was created in whole or in part by me and I
have the right to submit it under the open source license
indicated in the file; or
The contribution is based upon previous work that, to the best
of my knowledge, is covered under an appropriate open source
license and I have the right under that license to submit that
work with modifications, whether created in whole or in part
by me, under the same open source license (unless I am
permitted to submit under a different license), as indicated
in the file; or
- The contribution was provided directly to me by some other
person who certified (a), (b) or (c) and I have not modified
it.
- I understand and agree that this project and the contribution
are public and that a record of the contribution (including all
personal information I submit with it, including my sign-off) is
maintained indefinitely and may be redistributed consistent with
this project or the open source license(s) involved.
then you just add a line saying
This line can be automatically added by git if you run the git-commit
command with the -s option.
Notice that you can place your own Signed-off-by: line when
forwarding somebody else’s patch with the above rules for
D-C-O. Indeed you are encouraged to do so. Do not forget to
place an in-body “From: ” line at the beginning to properly attribute
the change to its true author (see above).
Also notice that a real name is used in the Signed-off-by: line. Please
don’t hide your real name.
If you like, you can put extra tags at the end:
- “Reported-by:” is used to to credit someone who found the bug that
the patch attempts to fix.
- “Acked-by:” says that the person who is more familiar with the area
the patch attempts to modify liked the patch.
- “Reviewed-by:”, unlike the other tags, can only be offered by the
reviewer and means that she is completely satisfied that the patch
is ready for application. It is usually offered only after a
detailed review.
- “Tested-by:” is used to indicate that the person applied the patch
and found it to have the desired effect.
You can also create your own tag or use one that’s in common usage
such as “Thanks-to:”, “Based-on-patch-by:”, or “Mentored-by:”.