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docker-offlineimap/docs/doc-src/GitAdvanced.rst
Nicolas Sebrecht e303c6c5d0 rework documentation 
- Add CONTRIBUTING.rst.
- Improve MAINTAINERS.rst.
- Split long HACKING.rst into:
  * dco.rst
  * GitAdvanced.rst

Update content.

Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>
2015-03-07 19:26:17 +01:00

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.. -*- coding: utf-8 -*-
.. _OfflineIMAP: http://offlineimap.org
.. _mailing list: http://lists.alioth.debian.org/mailman/listinfo/offlineimap-project
.. _Developers's Certificate of Origin: https://github.com/OfflineIMAP/offlineimap/blob/next/docs/doc-src/dco.rst
============
Git Advanced
============
.. contents:: :depth: 2
Git: OfflineImap's branching Model And Workflow
===============================================
Git Branching model
-------------------
OfflineIMAP_ uses the following branches:
master
This is **the mainline**. Simple users should use this branch.
next
**The development branch** for developers and testers. The content of ``next`` is
merged into the mainline ``master`` at release time for both stable and releases
candidates. When patches are sent to the mailing list, contributors discuss
about them. Once done and when patches looks ready for the mainline, patches
are first merged into ``next``. Advanced developers and testers use this branch to
test the last merged patches before they hit the mainline. This helps not
introducing strong breakages directly in the mainline.
maint
This is **the maintenance branch**. It gets its own releases starting off of an old
stable release.
Notice that this branch tend to be more or less abandoned when context does not
force the maintainers to take care of it.
pu
Don't care much about this branch unless you're asked to use it. It's almost
abandoned nowadays. ``pu`` stands for *"proposed updates"* and helps
**tracking of topics**. If a topic is not ready for the ``next`` release, it
might be merged into ``pu``. This branch only help developers to work on
someone else topic or an earlier pending topic. Developers can extract a topic
from this branch to work on it. This branch is **not intended to be
checkouted**; never. Even developers don't do that. Due to the way ``pu`` is
built you can't expect content there to work in any way... unless you clearly
want to run into troubles.
Release cycles
--------------
A typical release cycle works like this:
1. A stable release is out.
2. Feature topics are sent, discussed and merged.
3. When enough work was merged, we start the freeze cycle: the first release
candidate is out.
4. During the freeze cycle, no more features are merged. It's time to test
OfflineIMAP_. The more we are late in *-rc* releases, the less patches are
merged but bug fixes.
5. When we think a release is stable enough, we restart from step 1.
Because third-parties tend to not always follow the cycles, it's fine to send
your patches as soon as they are ready. Any maintainer might prefer to pend your
contributions before merging it at a better time. You'll always be notified if
such decision is made for your work.
Know about where we are in the release cycle::
$ git tag
Create commits
--------------
* Make commits of logical units.
* If you change, add, or remove a command line option or
make some other user interface change, the associated
documentation should be updated as well.
* Check for unnecessary whitespace with ``git diff --check``
before committing.
* Do not check in commented out code or unneeded files.
* the first line of the commit message should be a short
description (50 characters is the soft limit, see DISCUSSION
in git-commit(1)), and should skip the full stop
* The body should provide a meaningful commit message, which:
* uses the imperative, present tense: **change**,
not **changed** or **changes**;
* includes motivation for the change, and contrasts
its implementation with previous behaviour.
* Add a ``Signed-off-by: Your Name <you@example.com>`` line to
to confirm that you agree to the `Developer's Certificate of Origin`_.
* Make sure that you have tests for the bug you are fixing.
* Make sure that the test suite passes after your commit.
Make a pull request
-------------------
TODO.
Export commits as patches
-------------------------
* Use ``git format-patch -M`` to create the patch.
* Do not attach your patch, but read in the mail
body, unless you cannot teach your mailer to
leave the formatting of the patch alone.
* Be careful doing cut & paste into your mailer, not to
corrupt whitespaces.
Export commits as patches (experts)
-----------------------------------
* Do not PGP sign your patch.
* Provide additional information (which is unsuitable for
the commit message) between the ``---`` and the diffstat.
* If your name is not writable in ASCII, make sure that
you send off a message in the correct encoding.
* Send the patch to the `mailing list`_ if (and only if)
the patch is ready for inclusion.
* If you use `git-send-email(1)` which is a good idea,
please test it first by sending email to yourself.
* See below for instructions specific to your mailer.
Extract a topic from pu
-----------------------
To find the tip of a topic branch, run ``git log --first-parent next..pu`` and
look for the merge commit. The second parent of this commit is the tip of the
topic branch.
``pu`` is built this way::
$ git checkout pu
$ git reset --keep next
$ git merge --no-ff -X theirs topic1
$ git merge --no-ff -X theirs topic2
$ git merge --no-ff -X theirs blue
$ git merge --no-ff -X theirs orange
...
As a consequence:
1. Each topic merged uses a merge commit. A merge commit is a commit having 2
ancestors. Actually, Git allows more than 2 parents but we don't use this
feature. It's intended.
2. Paths in ``pu`` may mix up multiple versions if all the topics don't use the same
base commit. This is very often the case as topics aren't rebased: it guarantees
each topic is strictly identical to the last version sent to the mailing list.
No surprise.
What you need to extract a particular topic is the *sha1* of the tip of that
branch (the last commit of the topic). Assume you want the branch of the topic
called 'blue'. First, look at the log given by this command::
$ git log --reverse --merges --parents origin/next..origin/pu
With this command you ask for the log:
* from next to pu
* in reverse order (older first)
* merge commits only
* with the sha1 of the ancestors
From this list, find the topic you're looking for, basing you search on the lines
like::
Merge branch 'topic/name' into pu
By convention, it has the form <author_initials>/<brief_title>. When you're at
it, pick the topic ancestor sha1. It's always the last sha1 in the line starting
by 'commit'. For you to know:
* The first sha1 is the commit you see: the merge commit.
* The following sha1 is the ancestor of the branch checkouted at merge time
(always the previous merged topic or the ancien next in our case).
* Last is the branch merged.
Giving::
commit sha1_of_merge_commit sha1_of_ancient_pu sha1_of_topic_blue
Then, you only have to checkout the topic from there::
$ git checkout -b blue sha1_of_topic_blue
You're done! You've just created a new branch called "blue" with the blue
content. Be aware this topic is not updated against the **current** next branch.
,-)
Very detailed version
=====================
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
are only the relevant bits.
Decide what branch to base your work on
---------------------------------------
In general, base your work on the ``next`` branch. Otherwise, start off of the
latest commit your change is relevant to.
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.
Generate your patch using git tools out of your commits
-------------------------------------------------------
* ``git`` based diff tools (git, Cogito, and StGIT included) generate *unidiff*
which is the preferred format.
* You do not have to be afraid to use ``-M`` option to ``git diff`` or ``git
format-patch``, if your patch involves file renames. The receiving end can
handle them just fine.
* Please make sure your patch does not include any extra files which do not
belong in a patch submission.
* Make sure to review your patch after generating it, to ensure accuracy.
* Before sending out, please make sure it cleanly applies to the ``next`` branch
head. If you are preparing a work based on somewhere else, that is fine, but
please mark it as such.
Sending your patches
--------------------
The mailing list is the preferred way for sending patches. This allows easier
review and comments on the code.
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, 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.
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 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.
* 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:
An ideal patch flow
===================
Here is an ideal patch flow for this project the current maintainers
suggests to the contributors:
0. You come up with an itch. You code it up.
1. Send it to the list and cc people who may need to know about
the change.
The people who may need to know are the ones whose code you
are butchering. These people happen to be the ones who are
most likely to be knowledgeable enough to help you, but
they have no obligation to help you (i.e. you ask for help,
don't demand). ``git log -p -- $area_you_are_modifying`` would
help you find out who they are.
2. You get comments and suggestions for improvements. You may
even get them in a "on top of your change" patch form.
3. Polish, refine, and re-send to the list and the people who
spend their time to improve your patch. Go back to step (2).
4. The list forms consensus that the last round of your patch is
good. Send it to the list and cc the maintainers.
5. A topic branch is created with the patch and is merged to ``next``,
and cooked further and eventually graduates to ``master``.
In any time between the (2)-(3) cycle, the maintainer may pick it up
from the list and queue it to ``pu``, in order to make it easier for
people play with it without having to pick up and apply the patch to
their trees themselves.
Know the status of your patch after submission
----------------------------------------------
You can use Git itself to find out when your patch is merged in
master. ``git pull --rebase`` will automatically skip already-applied
patches, and will let you know. This works only if you rebase on top
of the branch in which your patch has been merged (i.e. it will not
tell you if your patch is merged in ``pu`` if you rebase on top of
``next``).
.. Read the git mailing list, the maintainer regularly posts messages
entitled "What's cooking in git.git" and "What's in git.git" giving
the status of various proposed changes.
MUA specific hints
==================
Some of patches I receive or pick up from the list share common
patterns of breakage. Please make sure your MUA is set up
properly not to corrupt whitespaces. Here are two common ones
I have seen:
* Empty context lines that do not have _any_ whitespace.
* Non empty context lines that have one extra whitespace at the
beginning.
One test you could do yourself if your MUA is set up correctly is:
* Send the patch to yourself, exactly the way you would, except
To: and Cc: lines, which would not contain the list and
maintainer address.
* Save that patch to a file in UNIX mailbox format. Call it say
a.patch.
* Try to apply to the tip of the "master" branch from the
git.git public repository::
$ git fetch http://kernel.org/pub/scm/git/git.git master:test-apply
$ git checkout test-apply
$ git reset --hard
$ git am a.patch
If it does not apply correctly, there can be various reasons.
* Your patch itself does not apply cleanly. That is _bad_ but
does not have much to do with your MUA. Please rebase the
patch appropriately.
* Your MUA corrupted your patch; "am" would complain that
the patch does not apply. Look at .git/rebase-apply/ subdirectory and
see what 'patch' file contains and check for the common
corruption patterns mentioned above.
* While you are at it, check what are in 'info' and
'final-commit' files as well. If what is in 'final-commit' is
not exactly what you would want to see in the commit log
message, it is very likely that your maintainer would end up
hand editing the log message when he applies your patch.
Things like "Hi, this is my first patch.\n", if you really
want to put in the patch e-mail, should come after the
three-dash line that signals the end of the commit message.
Pine
----
(Johannes Schindelin)
I don't know how many people still use pine, but for those poor souls it may
be good to mention that the quell-flowed-text is needed for recent versions.
... the "no-strip-whitespace-before-send" option, too. AFAIK it was introduced
in 4.60.
(Linus Torvalds)
And 4.58 needs at least this
::
---
diff-tree 8326dd8350be64ac7fc805f6563a1d61ad10d32c (from e886a61f76edf5410573e92e38ce22974f9c40f1)
Author: Linus Torvalds <torvalds@g5.osdl.org>
Date: Mon Aug 15 17:23:51 2005 -0700
Fix pine whitespace-corruption bug
There's no excuse for unconditionally removing whitespace from
the pico buffers on close.
diff --git a/pico/pico.c b/pico/pico.c
--- a/pico/pico.c
+++ b/pico/pico.c
@@ -219,7 +219,9 @@ PICO *pm;
switch(pico_all_done){ /* prepare for/handle final events */
case COMP_EXIT : /* already confirmed */
packheader();
+#if 0
stripwhitespace();
+#endif
c |= COMP_EXIT;
break;
(Daniel Barkalow)
> A patch to SubmittingPatches, MUA specific help section for
> users of Pine 4.63 would be very much appreciated.
Ah, it looks like a recent version changed the default behavior to do the
right thing, and inverted the sense of the configuration option. (Either
that or Gentoo did it.) So you need to set the
"no-strip-whitespace-before-send" option, unless the option you have is
"strip-whitespace-before-send", in which case you should avoid checking
it.
Thunderbird
-----------
(A Large Angry SCM)
By default, Thunderbird will both wrap emails as well as flag them as
being 'format=flowed', both of which will make the resulting email unusable
by git.
Here are some hints on how to successfully submit patches inline using
Thunderbird.
There are two different approaches. One approach is to configure
Thunderbird to not mangle patches. The second approach is to use
an external editor to keep Thunderbird from mangling the patches.
**Approach #1 (configuration):**
This recipe is current as of Thunderbird 2.0.0.19. Three steps:
1. Configure your mail server composition as plain text
Edit...Account Settings...Composition & Addressing,
uncheck 'Compose Messages in HTML'.
2. Configure your general composition window to not wrap
Edit..Preferences..Composition, wrap plain text messages at 0
3. Disable the use of format=flowed
Edit..Preferences..Advanced..Config Editor. Search for:
mailnews.send_plaintext_flowed
toggle it to make sure it is set to 'false'.
After that is done, you should be able to compose email as you
otherwise would (cut + paste, git-format-patch | git-imap-send, etc),
and the patches should not be mangled.
**Approach #2 (external editor):**
This recipe appears to work with the current [*1*] Thunderbird from Suse.
The following Thunderbird extensions are needed:
AboutConfig 0.5
http://aboutconfig.mozdev.org/
External Editor 0.7.2
http://globs.org/articles.php?lng=en&pg=8
1) Prepare the patch as a text file using your method of choice.
2) Before opening a compose window, use Edit->Account Settings to
uncheck the "Compose messages in HTML format" setting in the
"Composition & Addressing" panel of the account to be used to send the
patch. [*2*]
3) In the main Thunderbird window, _before_ you open the compose window
for the patch, use Tools->about:config to set the following to the
indicated values::
mailnews.send_plaintext_flowed => false
mailnews.wraplength => 0
4) Open a compose window and click the external editor icon.
5) In the external editor window, read in the patch file and exit the
editor normally.
6) Back in the compose window: Add whatever other text you wish to the
message, complete the addressing and subject fields, and press send.
7) Optionally, undo the about:config/account settings changes made in
steps 2 & 3.
[Footnotes]
*1* Version 1.0 (20041207) from the MozillaThunderbird-1.0-5 rpm of Suse
9.3 professional updates.
*2* It may be possible to do this with about:config and the following
settings but I haven't tried, yet::
mail.html_compose => false
mail.identity.default.compose_html => false
mail.identity.id?.compose_html => false
(Lukas Sandström)
There is a script in contrib/thunderbird-patch-inline which can help you
include patches with Thunderbird in an easy way. To use it, do the steps above
and then use the script as the external editor.
Gnus
----
'|' in the *Summary* buffer can be used to pipe the current
message to an external program, and this is a handy way to drive
"git am". However, if the message is MIME encoded, what is
piped into the program is the representation you see in your
*Article* buffer after unwrapping MIME. This is often not what
you would want for two reasons. It tends to screw up non ASCII
characters (most notably in people's names), and also
whitespaces (fatal in patches). Running 'C-u g' to display the
message in raw form before using '|' to run the pipe can work
this problem around.
KMail
-----
This should help you to submit patches inline using KMail.
1) Prepare the patch as a text file.
2) Click on New Mail.
3) Go under "Options" in the Composer window and be sure that
"Word wrap" is not set.
4) Use Message -> Insert file... and insert the patch.
5) Back in the compose window: add whatever other text you wish to the
message, complete the addressing and subject fields, and press send.
Gmail
-----
GMail does not appear to have any way to turn off line wrapping in the web
interface, so this will mangle any emails that you send. You can however
use "git send-email" and send your patches through the GMail SMTP server, or
use any IMAP email client to connect to the google IMAP server and forward
the emails through that.
To use ``git send-email`` and send your patches through the GMail SMTP server,
edit `~/.gitconfig` to specify your account settings::
[sendemail]
smtpencryption = tls
smtpserver = smtp.gmail.com
smtpuser = user@gmail.com
smtppass = p4ssw0rd
smtpserverport = 587
Once your commits are ready to be sent to the mailing list, run the
following commands::
$ git format-patch --cover-letter -M origin/master -o outgoing/
$ edit outgoing/0000-*
$ git send-email outgoing/*
To submit using the IMAP interface, first, edit your `~/.gitconfig` to specify your
account settings::
[imap]
folder = "[Gmail]/Drafts"
host = imaps://imap.gmail.com
user = user@gmail.com
pass = p4ssw0rd
port = 993
sslverify = false
You might need to instead use: folder = "[Google Mail]/Drafts" if you get an error
that the "Folder doesn't exist".
Once your commits are ready to be sent to the mailing list, run the
following commands::
$ git format-patch --cover-letter -M --stdout origin/master | git imap-send
Just make sure to disable line wrapping in the email client (GMail web
interface will line wrap no matter what, so you need to use a real
IMAP client).
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