===============

Committing code

===============

This section is addressed to the mergers and to anyone interested in knowing

how code gets committed into Django. If you're a community member who wants to

contribute code to Django, look at :doc:`writing-code/working-with-git` instead.

.. _handling-pull-requests:

Handling pull requests

======================

Since Django is hosted on GitHub, patches are provided in the form of pull

requests.

When committing a pull request, make sure each individual commit matches the

commit guidelines described below. Contributors are expected to provide the

best pull requests possible. In practice mergers - who will likely be more 

familiar with the commit guidelines - may decide to bring a commit up to

standard themselves.

You may want to have Jenkins or GitHub actions test the pull request with one

of the pull request builders that doesn't run automatically, such as Oracle or

Selenium. See the `CI wiki page`_ for instructions.

.. _CI wiki page: https://code.djangoproject.com/wiki/CI

If you find yourself checking out pull requests locally more often, this git

alias will be helpful::

    [alias]

        pr = !sh -c \"git fetch upstream pull/${1}/head:pr/${1} && git checkout pr/${1}\"

Add it to your ``~/.gitconfig``, and set ``upstream`` to be ``django/django``.

Then you can run ``git pr ####`` to checkout the corresponding pull request.

At this point, you can work on the code. Use ``git rebase -i`` and ``git

commit --amend`` to make sure the commits have the expected level of quality.

Once you're ready:

.. console::

    $ # Pull in the latest changes from main.

    $ git checkout main

    $ git pull upstream main

    $ # Rebase the pull request on main.

    $ git checkout pr/####

    $ git rebase main

    $ git checkout main

    $ # Merge the work as "fast-forward" to main to avoid a merge commit.

    $ # (in practice, you can omit "--ff-only" since you just rebased)

    $ git merge --ff-only pr/XXXX

    $ # If you're not sure if you did things correctly, check that only the

    $ # changes you expect will be pushed to upstream.

    $ git push --dry-run upstream main

    $ # Push!

    $ git push upstream main

    $ # Delete the pull request branch.

    $ git branch -d pr/xxxx

Force push to the branch after rebasing on main but before merging and pushing

to upstream. This allows the commit hashes on main and the branch to match

which automatically closes the pull request.

If a pull request doesn't need to be merged as multiple commits, you can use

GitHub's "Squash and merge" button on the website. Edit the commit message as

needed to conform to :ref:`the guidelines <committing-guidelines>` and remove

the pull request number that's automatically appended to the message's first

line.

When rewriting the commit history of a pull request, the goal is to make

Django's commit history as usable as possible:

* If a patch contains back-and-forth commits, then rewrite those into one.

  For example, if a commit adds some code and a second commit fixes stylistic

  issues introduced in the first commit, those commits should be squashed

  before merging.

* Separate changes to different commits by logical grouping: if you do a

  stylistic cleanup at the same time as you do other changes to a file,

  separating the changes into two different commits will make reviewing

  history easier.

* Beware of merges of upstream branches in the pull requests.

* Tests should pass and docs should build after each commit. Neither the

  tests nor the docs should emit warnings.

* Trivial and small patches usually are best done in one commit. Medium to

  large work may be split into multiple commits if it makes sense.

Practicality beats purity, so it is up to each merger to decide how much

history mangling to do for a pull request. The main points are engaging the

community, getting work done, and having a usable commit history.

.. _committing-guidelines:

Committing guidelines

=====================

In addition, please follow the following guidelines when committing code to

Django's Git repository:

* Never change the published history of ``django/django`` branches by force

  pushing. If you absolutely must (for security reasons for example), first

  discuss the situation with the team.

* For any medium-to-big changes, where "medium-to-big" is according to

  your judgment, please bring things up on the |django-developers|

  mailing list before making the change.

  If you bring something up on |django-developers| and nobody responds,

  please don't take that to mean your idea is great and should be

  implemented immediately because nobody contested it. Everyone doesn't always

  have a lot of time to read mailing list discussions immediately, so you may

  have to wait a couple of days before getting a response.

* Write detailed commit messages in the past tense, not present tense.

  * Good: "Fixed Unicode bug in RSS API."

  * Bad: "Fixes Unicode bug in RSS API."

  * Bad: "Fixing Unicode bug in RSS API."

  The commit message should be in lines of 72 chars maximum. There should be

  a subject line, separated by a blank line and then paragraphs of 72 char

  lines. The limits are soft. For the subject line, shorter is better. In the

  body of the commit message more detail is better than less:

  .. code-block:: none

      Fixed #18307 -- Added git workflow guidelines.

      Refactored the Django's documentation to remove mentions of SVN

      specific tasks. Added guidelines of how to use Git, GitHub, and

      how to use pull request together with Trac instead.

  Credit the contributors in the commit message: "Thanks A for the report and B

  for review." Use git's `Co-Authored-By`_ as appropriate.

  .. _Co-Authored-By: https://docs.github.com/en/pull-requests/committing-changes-to-your-project/creating-and-editing-commits/creating-a-commit-with-multiple-authors

* For commits to a branch, prefix the commit message with the branch name.

  For example: "[1.4.x] Fixed #xxxxx -- Added support for mind reading."

* Limit commits to the most granular change that makes sense. This means,

  use frequent small commits rather than infrequent large commits. For

  example, if implementing feature X requires a small change to library Y,

  first commit the change to library Y, then commit feature X in a separate

  commit. This goes a *long way* in helping everyone follow your changes.

* Separate bug fixes from feature changes. Bugfixes may need to be backported

  to the stable branch, according to :ref:`supported-versions-policy`.

* If your commit closes a ticket in the Django `ticket tracker`_, begin

  your commit message with the text "Fixed #xxxxx", where "xxxxx" is the

  number of the ticket your commit fixes. Example: "Fixed #123 -- Added

  whizbang feature.". We've rigged Trac so that any commit message in that

  format will automatically close the referenced ticket and post a comment

  to it with the full commit message.

  For the curious, we're using a `Trac plugin`_ for this.

.. note::

    Note that the Trac integration doesn't know anything about pull requests.

    So if you try to close a pull request with the phrase "closes #400" in your

    commit message, GitHub will close the pull request, but the Trac plugin

    will not close the same numbered ticket in Trac.

.. _Trac plugin: https://github.com/trac-hacks/trac-github

* If your commit references a ticket in the Django `ticket tracker`_ but

  does *not* close the ticket, include the phrase "Refs #xxxxx", where "xxxxx"

  is the number of the ticket your commit references. This will automatically

  post a comment to the appropriate ticket.

* Write commit messages for backports using this pattern:

  .. code-block:: none

    [<Django version>] Fixed <ticket> -- <description>

    Backport of <revision> from <branch>.

  For example:

  .. code-block:: none

    [1.3.x] Fixed #17028 -- Changed diveintopython.org -> diveintopython.net.

    Backport of 80c0cbf1c97047daed2c5b41b296bbc56fe1d7e3 from main.

  There's a `script on the wiki

  <https://code.djangoproject.com/wiki/MergerTips#AutomatingBackports>`_ to

  automate this.

  If the commit fixes a regression, include this in the commit message:

  .. code-block:: none

    Regression in 6ecccad711b52f9273b1acb07a57d3f806e93928.

  (use the commit hash where the regression was introduced).

Reverting commits

=================

Nobody's perfect; mistakes will be committed.

But try very hard to ensure that mistakes don't happen. Just because we have a

reversion policy doesn't relax your responsibility to aim for the highest

quality possible. Really: double-check your work, or have it checked by

another merger **before** you commit it in the first place!

When a mistaken commit is discovered, please follow these guidelines:

* If possible, have the original author revert their own commit.

* Don't revert another author's changes without permission from the

  original author.

* Use git revert -- this will make a reverse commit, but the original

  commit will still be part of the commit history.

* If the original author can't be reached (within a reasonable amount

  of time -- a day or so) and the problem is severe -- crashing bug,

  major test failures, etc. -- then ask for objections on the

  |django-developers| mailing list then revert if there are none.

* If the problem is small (a feature commit after feature freeze,

  say), wait it out.

* If there's a disagreement between the merger and the reverter-to-be then try

  to work it out on the |django-developers| mailing list. If an agreement can't

  be reached then it should be put to a vote.

* If the commit introduced a confirmed, disclosed security

  vulnerability then the commit may be reverted immediately without

  permission from anyone.

* The release branch maintainer may back out commits to the release

  branch without permission if the commit breaks the release branch.

* If you mistakenly push a topic branch to ``django/django``, delete it.

  For instance, if you did: ``git push upstream feature_antigravity``,

  do a reverse push: ``git push upstream :feature_antigravity``.

.. _ticket tracker: https://code.djangoproject.com/