275 lines
10 KiB
Plaintext
275 lines
10 KiB
Plaintext
Working with Git and GitHub
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===========================
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This section explains how the community can contribute code to Django via pull
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requests. If you're interested in how core developers handle them, see
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:doc:`../committing-code`.
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Below, we are going to show how to create a GitHub pull request containing the
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changes for Trac ticket #xxxxx. By creating a fully-ready pull request you
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will make the reviewer's job easier, meaning that your work is more likely to
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be merged into Django.
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You could also upload a traditional patch to Trac, but it's less practical for
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reviews.
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Installing Git
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--------------
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Django uses `Git`_ for its source control. You can `download
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<http://git-scm.com/download>`_ Git, but it's often easier to install with
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your operating system's package manager.
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Django's `Git repository`_ is hosted on `GitHub`_, and it is recommended
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that you also work using GitHub.
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After installing Git the first thing you should do is setup your name and
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email::
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$ git config --global user.name "Your Real Name"
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$ git config --global user.email "you@email.com"
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Note that ``user.name`` should be your real name, not your GitHub nick. GitHub
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should know the email you use in the ``user.email`` field, as this will be
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used to associate your commits with your GitHub account.
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.. _Git: http://git-scm.com/
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.. _Git repository: https://github.com/django/django/
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.. _GitHub: https://github.com/
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Setting up local repository
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---------------------------
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When you have created your GitHub account, with the nick "github_nick", and
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forked Django's repository, create a local copy of your fork::
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git clone git@github.com:github_nick/django.git
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This will create a new directory "django", containing a clone of your GitHub
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repository. The rest of the git commands on this page need to be run within the
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cloned directory so switch to it now::
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cd django
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Your GitHub repository will be called "origin" in Git.
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You should also setup django/django as an "upstream" remote (that is, tell git
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that the reference Django repository was the source of your fork of it)::
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git remote add upstream git@github.com:django/django.git
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git fetch upstream
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You can add other remotes similarly, for example::
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git remote add akaariai git@github.com:akaariai/django.git
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Working on a ticket
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-------------------
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When working on a ticket create a new branch for the work, and base that work
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on upstream/master::
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git checkout -b ticket_xxxxx upstream/master
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The -b flag creates a new branch for you locally. Don't hesitate to create new
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branches even for the smallest things - that's what they are there for.
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If instead you were working for a fix on the 1.4 branch, you would do::
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git checkout -b ticket_xxxxx_1_4 upstream/stable/1.4.x
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Assume the work is carried on ticket_xxxxx branch. Make some changes and
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commit them::
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git commit
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When writing the commit message, follow the :ref:`commit message
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guidelines <committing-guidelines>` to ease the work of the committer. If
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you're uncomfortable with English, try at least to describe precisely what the
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commit does.
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If you need to do additional work on your branch, commit as often as
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necessary::
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git commit -m 'Added two more tests for edge cases'
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Publishing work
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~~~~~~~~~~~~~~~
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You can publish your work on GitHub just by doing::
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git push origin ticket_xxxxx
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When you go to your GitHub page you will notice a new branch has been created.
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If you are working on a Trac ticket, you should mention in the ticket that
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your work is available from branch ticket_xxxxx of your github repo. Include a
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link to your branch.
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Note that the above branch is called a "topic branch" in Git parlance. You are
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free to rewrite the history of this branch, by using ``git rebase`` for
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example. Other people shouldn't base their work on such a branch, because
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their clone would become corrupt when you edit commits.
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There are also "public branches". These are branches other people are supposed
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to fork, so the history of these branches should never change. Good examples
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of public branches are the ``master`` and ``stable/A.B.x`` branches in the
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django/django repository.
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When you think your work is ready to be pulled into Django, you should create
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a pull request at GitHub. A good pull request means:
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* commits with one logical change in each, following the
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:doc:`coding style <coding-style>`,
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* well-formed messages for each commit: a summary line and then paragraphs
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wrapped at 72 characters thereafter -- see the :ref:`committing guidelines
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<committing-guidelines>` for more details,
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* documentation and tests, if needed -- actually tests are always needed,
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except for documentation changes.
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The test suite must pass and the documentation must build without warnings.
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Once you have created your pull request, you should add a comment in the
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related Trac ticket explaining what you've done. In particular you should note
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the environment in which you ran the tests, for instance: "all tests pass
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under SQLite and MySQL".
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Pull requests at GitHub have only two states: open and closed. The committer
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who will deal with your pull request has only two options: merge it or close
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it. For this reason, it isn't useful to make a pull request until the code is
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ready for merging -- or sufficiently close that a committer will finish it
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himself.
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Rebasing branches
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~~~~~~~~~~~~~~~~~
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In the example above you created two commits, the "Fixed ticket_xxxxx" commit
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and "Added two more tests" commit.
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We do not want to have the entire history of your working process in your
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repository. Your commit "Added two more tests" would be unhelpful noise.
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Instead, we would rather only have one commit containing all your work.
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To rework the history of your branch you can squash the commits into one by
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using interactive rebase::
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git rebase -i HEAD~2
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The HEAD~2 above is shorthand for two latest commits. The above command
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will open an editor showing the two commits, prefixed with the word "pick".
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Change "pick" on the second line to "squash" instead. This will keep the
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first commit, and squash the second commit into the first one. Save and quit
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the editor. A second editor window should open, so you can reword the
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commit message for the commit now that it includes both your steps.
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You can also use the "edit" option in rebase. This way you can change a single
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commit, for example to fix a typo in a docstring::
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git rebase -i HEAD~3
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# Choose edit, pick, pick for the commits
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# Now you are able to rework the commit (use git add normally to add changes)
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# When finished, commit work with "--amend" and continue
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git commit --amend
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# reword the commit message if needed
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git rebase --continue
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# The second and third commits should be applied.
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If your topic branch is already published at GitHub, for example if you're
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making minor changes to take into account a review, you will need to force-
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push the changes::
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git push -f origin ticket_xxxxx
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Note that this will rewrite history of ticket_xxxxx - if you check the commit
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hashes before and after the operation at GitHub you will notice that the
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commit hashes do not match any more. This is acceptable, as the branch is merely
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a topic branch, and nobody should be basing their work on it.
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After upstream has changed
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~~~~~~~~~~~~~~~~~~~~~~~~~~
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When upstream (django/django) has changed, you should rebase your work. To
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do this, use::
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git fetch upstream
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git rebase
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The work is automatically rebased using the branch you forked on, in the
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example case using upstream/master.
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The rebase command removes all your local commits temporarily, applies the
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upstream commits, and then applies your local commits again on the work.
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If there are merge conflicts you will need to resolve them and then use ``git
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rebase --continue``. At any point you can use ``git rebase --abort`` to return
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to the original state.
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Note that you want to *rebase* on upstream, not *merge* the upstream.
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The reason for this is that by rebasing, your commits will always be *on
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top of* the upstream's work, not *mixed in with* the changes in the upstream.
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This way your branch will contain only commits related to its topic, which
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makes squashing easier.
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After review
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~~~~~~~~~~~~
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It is unusual to get any non-trivial amount of code into core without changes
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requested by reviewers. In this case, it is often a good idea to add the
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changes as one incremental commit to your work. This allows the reviewer to
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easily check what changes you have done.
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In this case, do the changes required by the reviewer. Commit as often as
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necessary. Before publishing the changes, rebase your work. If you added two
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commits, you would run::
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git rebase -i HEAD~2
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Squash the second commit into the first. Write a commit message along the lines
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of::
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Made changes asked in review by <reviewer>
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- Fixed whitespace errors in foobar
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- Reworded the docstring of bar()
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Finally push your work back to your GitHub repository. Since you didn't touch
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the public commits during the rebase, you should not need to force-push::
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git push origin ticket_xxxxx
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Your pull request should now contain the new commit too.
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Note that the committer is likely to squash the review commit into the previous
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commit when committing the code.
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Working on a patch
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------------------
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One of the ways that developers can contribute to Django is by reviewing
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patches. Those patches will typically exist as pull requests on GitHub and
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can be easily integrated into your local repository::
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git checkout -b pull_xxxxx upstream/master
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curl https://github.com/django/django/pull/xxxxx.patch | git am
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This will create a new branch and then apply the changes from the pull request
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to it. At this point you can run the tests or do anything else you need to
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do to investigate the quality of the patch.
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For more detail on working with pull requests see the
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:ref:`guidelines for committers <handling-pull-requests>`.
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Summary
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-------
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* Work on GitHub if you can.
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* Announce your work on the Trac ticket by linking to your GitHub branch.
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* When you have something ready, make a pull request.
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* Make your pull requests as good as you can.
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* When doing fixes to your work, use ``git rebase -i`` to squash the commits.
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* When upstream has changed, do ``git fetch upstream; git rebase``.
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