.. _using-git:


Contributing to *mne-python* source code
========================================

We are open to all types of contributions, from bugfixes to functionality
enhancements. mne-python_ is meant to be maintained by a community of labs,
and as such, we seek enhancements that will likely benefit a large proportion
of the users who use the package.

*Before starting new code*, we highly recommend opening an issue on
`mne-python GitHub`_ to discuss potential changes. Getting on the same
page as the maintainers about changes or enhancements before too much
coding is done saves everyone time and effort!

What you will need
------------------

#. A Unix (Linux or Mac OS) box: `MNE command line utilities`_ and Freesurfer_
   that are required to make the best out of this toolbox require a Unix platform.

#. A good python editor: Spyder_ IDE is suitable for those migrating from
   Matlab. EPD_ and Anaconda_ both ship Spyder and all its dependencies. For
   Mac users, TextMate_ and `Sublime Text`_ are good choices. `Sublime Text`_
   is available on all three major platforms.

#. Basic scientific tools in python: numpy_, scipy_, matplotlib_

#. Development related tools: nosetests_, coverage_, mayavi_, sphinx_,
   pep8_, and pyflakes_

#. Other useful packages: pysurfer_, nitime_, pandas_, PIL_, PyDICOM_,
   joblib_, nibabel_, and scikit-learn_

#. External tools: `MNE command line utilities`_, Freesurfer_, and `mne-scripts`_

General code guidelines
-----------------------

* We highly recommend using a code editor that uses both `pep8`_ and
  `pyflakes`_, such as `spyder`_. Standard python style guidelines are
  followed, with very few exceptions.

  You can also manually check pyflakes and pep8 warnings as::

       pip install pyflakes
       pip install pep8
       pyflakes path/to/module.py
       pep8 path/to/module.py

  AutoPEP8 can then help you fix some of the easy redundant errors::

       pip install autopep8
       autopep8 path/to/pep8.py

* mne-python adheres to the same docstring formatting as seen on
  `numpy style`_.
  New public functions should have all variables defined.

* New functionality should be covered by appropriate tests, e.g. a method in
  ``mne/fiff/raw.py`` should have a corresponding test in
  ``mne/fiff/tests/test_raw.py``. You can use the ``coverage`` module in
  conjunction with ``nosetests`` (nose can automatically determine the code
  coverage if ``coverage`` is installed) to see how well new code is covered.

* After changes have been made, **ensure all tests pass**. This can be done
  by running the following from the ``mne-python`` root directory::

     make

  To run individual tests, you can also run any of the following::

     make clean
     make inplace
     make test-doc
     make inplace
     nosetests

  Note that the first time this is run, the `mne-python sample dataset`_
  (~1.2 GB) will be downloaded to the root directory and extracted. This is
  necessary for running some of the tests and nearly all of the examples.

  You can also run ``nosetests -x`` to have nose stop as soon as a failed
  test is found, or run e.g., ``nosetests mne/fiff/tests/test_raw.py`` to run
  a specific test.

Configuring git
---------------

Any contributions to the core mne-python package, whether bug fixes,
improvements to the documentation, or new functionality, can be done via
*pull requests* on GitHub. The workflow for this is described here.
[Many thanks to Astropy_ for providing clear instructions that we have
adapted for our use here!]

The only absolutely necessary configuration step is identifying yourself and
your contact info::

     git config --global user.name "Your Name"
     git config --global user.email you@yourdomain.example.com

If you are going to :ref:`setup-github` eventually, this email address should
be the same as the one used to sign up for a GitHub account. For more
information about configuring your git installation, see
:ref:`customizing-git`.

The following sections cover the installation of the git software, the basic
configuration, and links to resources to learn more about using git.
However, you can also directly go to the `GitHub help pages
<http://help.github.com/>`_ which offer a great introduction to git and
GitHub.

In the present document, we refer to the mne-python ``master`` branch, as the
*trunk*.

.. _forking:

Creating a fork
^^^^^^^^^^^^^^^

You need to do this only once for each package you want to contribute to. The
instructions here are very similar to the instructions at
http://help.github.com/fork-a-repo/ |emdash| please see that page for more
details. We're repeating some of it here just to give the specifics for the
mne-python_ project, and to suggest some default names.

.. _setup-github:

Set up and configure a GitHub account
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

If you don't have a GitHub account, go to the GitHub page, and make one.

You then need to configure your account to allow write access |emdash| see
the *Generating SSH keys* help on `GitHub Help`_.

Create your own fork of a repository
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Now you should fork the core ``mne-python`` repository (although you could
in principle also fork a different one, such as ``mne-matlab```):

#. Log into your GitHub account.

#. Go to the `mne-python GitHub`_ home.

#. Click on the *fork* button:

   .. image:: _static/forking_button.png

   Now, after a short pause and some 'Hardcore forking action', you should
   find yourself at the home page for your own forked copy of mne-python_.

Setting up the fork and the working directory
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Briefly, this is done using::

    git clone git@github.com:your-user-name/mne-python.git
    cd mne-python
    git remote add upstream git://github.com/mne-tools/mne-python.git

These steps can be broken out to be more explicit as:

#. Clone your fork to the local computer::

    git clone git@github.com:your-user-name/mne-python.git

#. Create a symbolic link to your mne directory::

   To find the directory in which python packages are installed, go to python
   and type::

    import site; site.getsitepackages()

   This gives two directories::

    ['/usr/local/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages']

   When you write examples and import the MNE modules, this is where python
   searches and imports them from. If you want to avoid installing the
   package again when you make changes in your source code, it is better to
   create a symbolic link from the installation directory to the ``mne/``
   folder containing your source code.

   First, check if there are any ``mne`` or ``mne-*.egg-info`` files in
   these directories and delete them. Then, find the user directory for
   installing python packages::

    import site; site.getusersitepackages()

   This might give for instance::

    '~/.local/lib/python2.7/site-packages'

   Then, make a symbolic link to your working directory::

    ln -s <path to mne-python>/mne ~/.local/lib/python2.7/site-packages/mne

   Since you make a symbolic link to the local directory, you won't require
   root access while editing the files and the changes in your working
   directory are automatically reflected in the installation directory. To
   verify that it works, go to a directory other than the installation
   directory, run ipython, and then type ``import mne; print mne.__path__``.
   This will show you from where it imported MNE-Python.

   Now, whenever you make any changes to the code, just restart the
   ipython kernel for the changes to take effect.

#. Change directory to your new repo::

    cd mne-python

   Then type::

    git branch -a

   to show you all branches.  You'll get something like::

    * master
    remotes/origin/master

   This tells you that you are currently on the ``master`` branch, and
   that you also have a ``remote`` connection to ``origin/master``.
   What remote repository is ``remote/origin``? Try ``git remote -v`` to
   see the URLs for the remote.  They will point to your GitHub fork.

   Now you want to connect to the mne-python repository, so you can
   merge in changes from the trunk::

    cd mne-python
    git remote add upstream git://github.com/mne-tools/mne-python.git

   ``upstream`` here is just the arbitrary name we're using to refer to the
   main mne-python_ repository.

   Note that we've used ``git://`` for the URL rather than ``git@``. The
   ``git://`` URL is read only. This means we that we can't accidentally (or
   deliberately) write to the upstream repo, and we are only going to use it
   to merge into our own code.

   Just for your own satisfaction, show yourself that you now have a new
   'remote', with ``git remote -v show``, giving you something like::

    upstream   git://github.com/mne-tools/mne-python.git (fetch)
    upstream   git://github.com/mne-tools/mne-python.git (push)
    origin     git@github.com:your-user-name/mne-python.git (fetch)
    origin     git@github.com:your-user-name/mne-python.git (push)

   Your fork is now set up correctly.

#. Ensure unit tests pass and html files can be compiled

   Make sure before starting to code that all unit tests pass and the
   html files in the ``doc/`` directory can be built without errors. To build
   the html files, first go the ``doc/`` directory and then type::

    make html

   Once it is compiled for the first time, subsequent compiles will only
   recompile what has changed. That's it! You are now ready to hack away.

Workflow summary
----------------

This section gives a summary of the workflow once you have successfully forked
the repository, and details are given for each of these steps in the following
sections.

* Don't use your ``master`` branch for anything.  Consider deleting it.

* When you are starting a new set of changes, fetch any changes from the
  trunk, and start a new *feature branch* from that.

* Make a new branch for each separable set of changes |emdash| "one task, one
  branch" (`ipython git workflow`_).

* Name your branch for the purpose of the changes - e.g.
  ``bugfix-for-issue-14`` or ``refactor-database-code``.

* If you can possibly avoid it, avoid merging trunk or any other branches into
  your feature branch while you are working.

* If you do find yourself merging from the trunk, consider :ref:`rebase-on-trunk`

* **Ensure all tests still pass**

* Ask for code review!

This way of working helps to keep work well organized, with readable history.
This in turn makes it easier for project maintainers (that might be you) to
see what you've done, and why you did it.

See `linux git workflow`_ and `ipython git workflow`_ for some explanation.

Deleting your master branch
^^^^^^^^^^^^^^^^^^^^^^^^^^^

It may sound strange, but deleting your own ``master`` branch can help reduce
confusion about which branch you are on.  See `deleting master on github`_ for
details.

.. _update-mirror-trunk:

Updating the mirror of trunk
^^^^^^^^^^^^^^^^^^^^^^^^^^^^

From time to time you should fetch the upstream (trunk) changes from GitHub::

   git fetch upstream

This will pull down any commits you don't have, and set the remote branches to
point to the right commit. For example, 'trunk' is the branch referred to by
(remote/branchname) ``upstream/master`` - and if there have been commits since
you last checked, ``upstream/master`` will change after you do the fetch.

.. _make-feature-branch:

Making a new feature branch
^^^^^^^^^^^^^^^^^^^^^^^^^^^

When you are ready to make some changes to the code, you should start a new
branch. Branches that are for a collection of related edits are often called
'feature branches'.

Making an new branch for each set of related changes will make it easier for
someone reviewing your branch to see what you are doing.

Choose an informative name for the branch to remind yourself and the rest of
us what the changes in the branch are for. For example ``add-ability-to-fly``,
or ``buxfix-for-issue-42``.

::

    # Update the mirror of trunk
    git fetch upstream

    # Make new feature branch starting at current trunk
    git branch my-new-feature upstream/master
    git checkout my-new-feature

Generally, you will want to keep your feature branches on your public GitHub_
fork. To do this, you `git push`_ this new branch up to your
github repo. Generally (if you followed the instructions in these pages, and
by default), git will have a link to your GitHub repo, called ``origin``. You
push up to your own repo on GitHub with::

   git push origin my-new-feature

In git > 1.7 you can ensure that the link is correctly set by using the
``--set-upstream`` option::

   git push --set-upstream origin my-new-feature

From now on git will know that ``my-new-feature`` is related to the
``my-new-feature`` branch in the GitHub repo.

.. _edit-flow:

The editing workflow
--------------------

Overview
^^^^^^^^

::

   git add my_new_file
   git commit -am 'FIX: some message'
   git push

In more detail
^^^^^^^^^^^^^^

#. Make some changes

#. See which files have changed with ``git status`` (see `git status`_).
   You'll see a listing like this one::

     # On branch ny-new-feature
     # Changed but not updated:
     #   (use "git add <file>..." to update what will be committed)
     #   (use "git checkout -- <file>..." to discard changes in working directory)
     #
     #    modified:   README
     #
     # Untracked files:
     #   (use "git add <file>..." to include in what will be committed)
     #
     #    INSTALL
     no changes added to commit (use "git add" and/or "git commit -a")

#. Check what the actual changes are with ``git diff`` (`git diff`_).

#. Add any new files to version control ``git add new_file_name`` (see
   `git add`_).

#. Add any modified files that you want to commit using
   ``git add modified_file_name``  (see `git add`_).

#. Once you are ready to commit, check with ``git status`` which files are
   about to be committed::

    # Changes to be committed:
    #   (use "git reset HEAD <file>..." to unstage)
    #
    #    modified:   README

   Then use ``git commit -m 'A commit message'``. The ``m`` flag just
   signals that you're going to type a message on the command line. The `git
   commit`_ manual page might also be useful.

   It is also good practice to prefix commits with the type of change, such as
   ``FIX:``, ``STY:``, or ``ENH:`` for fixes, style changes, or enhancements.

#. To push the changes up to your forked repo on GitHub, do a ``git
   push`` (see `git push`_).

Asking for your changes to be reviewed or merged
------------------------------------------------

When you are ready to ask for someone to review your code and consider a merge:

#. Go to the URL of your forked repo, say
   ``http://github.com/your-user-name/mne-python``.

#. Use the 'Switch Branches' dropdown menu near the top left of the page to
   select the branch with your changes:

   .. image:: _static/branch_dropdown.png

#. Click on the 'Pull request' button:

   .. image:: _static/pull_button.png

   Enter a title for the set of changes, and some explanation of what you've
   done. Say if there is anything you'd like particular attention for - like a
   complicated change or some code you are not happy with.

   If you don't think your request is ready to be merged, prefix ``WIP:`` to
   the title of the pull request, and note it also in your pull request
   message. This is still a good way of getting some preliminary code review.
   Submitting a pull request early on in feature development can save a great
   deal of time for you, as the code maintainers may have "suggestions" about
   how the code should be written (features, style, etc.) that are easier to
   implement from the start.

If you are uncertain about what would or would not be appropriate to contribute
to mne-python, don't hesitate to either send a pull request, or open an issue
on the mne-python_ GitHub site to discuss potential changes.

Some other things you might want to do
--------------------------------------

Delete a branch on GitHub
^^^^^^^^^^^^^^^^^^^^^^^^^

::

   # change to the master branch (if you still have one, otherwise change to another branch)
   git checkout master

   # delete branch locally
   git branch -D my-unwanted-branch

   # delete branch on GitHub
   git push origin :my-unwanted-branch

(Note the colon ``:`` before ``test-branch``.  See also:
http://github.com/guides/remove-a-remote-branch

Several people sharing a single repository
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

If you want to work on some stuff with other people, where you are all
committing into the same repository, or even the same branch, then just
share it via GitHub.

First fork mne-python into your account, as from :ref:`forking`.

Then, go to your forked repository GitHub page, say
``http://github.com/your-user-name/mne-python``

Click on the 'Admin' button, and add anyone else to the repo as a
collaborator:

   .. image:: _static/pull_button.png

Now all those people can do::

    git clone git@githhub.com:your-user-name/mne-python.git

Remember that links starting with ``git@`` use the ssh protocol and are
read-write; links starting with ``git://`` are read-only.

Your collaborators can then commit directly into that repo with the
usual::

     git commit -am 'ENH: much better code'
     git push origin master # pushes directly into your repo

Explore your repository
^^^^^^^^^^^^^^^^^^^^^^^

To see a graphical representation of the repository branches and
commits::

   gitk --all

To see a linear list of commits for this branch::

   git log

You can also look at the `network graph visualizer`_ for your GitHub
repo.

Finally the ``lg`` alias will give you a reasonable text-based graph of the
repository.

If you are making extensive changes, ``git grep`` is also very handy.

.. _rebase-on-trunk:

Rebasing on trunk
^^^^^^^^^^^^^^^^^

Let's say you thought of some work you'd like to do. You
:ref:`update-mirror-trunk` and :ref:`make-feature-branch` called
``cool-feature``. At this stage trunk is at some commit, let's call it E. Now
you make some new commits on your ``cool-feature`` branch, let's call them A,
B, C. Maybe your changes take a while, or you come back to them after a while.
In the meantime, trunk has progressed from commit E to commit (say) G::

          A---B---C cool-feature
         /
    D---E---F---G trunk

At this stage you consider merging trunk into your feature branch, and you
remember that this here page sternly advises you not to do that, because the
history will get messy. Most of the time you can just ask for a review, and
not worry that trunk has got a little ahead. But sometimes, the changes in
trunk might affect your changes, and you need to harmonize them. In this
situation you may prefer to do a rebase.

Rebase takes your changes (A, B, C) and replays them as if they had been made
to the current state of ``trunk``. In other words, in this case, it takes the
changes represented by A, B, C and replays them on top of G. After the rebase,
your history will look like this::

                  A'--B'--C' cool-feature
                 /
    D---E---F---G trunk

See `rebase without tears`_ for more detail.

To do a rebase on trunk::

    # Update the mirror of trunk
    git fetch upstream

    # Go to the feature branch
    git checkout cool-feature

    # Make a backup in case you mess up
    git branch tmp cool-feature

    # Rebase cool-feature onto trunk
    git rebase --onto upstream/master upstream/master cool-feature

In this situation, where you are already on branch ``cool-feature``, the last
command can be written more succinctly as::

    git rebase upstream/master

When all looks good you can delete your backup branch::

   git branch -D tmp

If it doesn't look good you may need to have a look at
:ref:`recovering-from-mess-up`.

If you have made changes to files that have also changed in trunk, this may
generate merge conflicts that you need to resolve - see the `git rebase`_ man
page for some instructions at the end of the "Description" section. There is
some related help on merging in the git user manual - see `resolving a
merge`_.

If your feature branch is already on GitHub and you rebase, you will have to force
push the branch; a normal push would give an error. If the branch you rebased is
called ``cool-feature`` and your GitHub fork is available as the remote called ``origin``,
you use this command to force-push::

   git push -f origin cool-feature

Note that this will overwrite the branch on GitHub, i.e. this is one of the few ways
you can actually lose commits with git.
Also note that it is never allowed to force push to the main mne-python repo (typically
called ``upstream``), because this would re-write commit history and thus cause problems
for all others.

.. _recovering-from-mess-up:

Recovering from mess-ups
^^^^^^^^^^^^^^^^^^^^^^^^

Sometimes, you mess up merges or rebases. Luckily, in git it is relatively
straightforward to recover from such mistakes.

If you mess up during a rebase::

   git rebase --abort

If you notice you messed up after the rebase::

   # Reset branch back to the saved point
   git reset --hard tmp

If you forgot to make a backup branch::

   # Look at the reflog of the branch
   git reflog show cool-feature

   8630830 cool-feature@{0}: commit: BUG: io: close file handles immediately
   278dd2a cool-feature@{1}: rebase finished: refs/heads/my-feature-branch onto 11ee694744f2552d
   26aa21a cool-feature@{2}: commit: BUG: lib: make seek_gzip_factory not leak gzip obj
   ...

   # Reset the branch to where it was before the botched rebase
   git reset --hard cool-feature@{2}

Otherwise, googling the issue may be helpful (especially links to Stack
Overflow).

.. _rewriting-commit-history:

Rewriting commit history
^^^^^^^^^^^^^^^^^^^^^^^^

.. note::

   Do this only for your own feature branches.

There's an embarrassing typo in a commit you made? Or perhaps the you
made several false starts you would like the posterity not to see.

This can be done via *interactive rebasing*.

Suppose that the commit history looks like this::

    git log --oneline
    eadc391 Fix some remaining bugs
    a815645 Modify it so that it works
    2dec1ac Fix a few bugs + disable
    13d7934 First implementation
    6ad92e5 * masked is now an instance of a new object, MaskedConstant
    29001ed Add pre-nep for a copule of structured_array_extensions.
    ...

and ``6ad92e5`` is the last commit in the ``cool-feature`` branch. Suppose we
want to make the following changes:

* Rewrite the commit message for ``13d7934`` to something more sensible.
* Combine the commits ``2dec1ac``, ``a815645``, ``eadc391`` into a single one.

We do as follows::

    # make a backup of the current state
    git branch tmp HEAD
    # interactive rebase
    git rebase -i 6ad92e5

This will open an editor with the following text in it::

    pick 13d7934 First implementation
    pick 2dec1ac Fix a few bugs + disable
    pick a815645 Modify it so that it works
    pick eadc391 Fix some remaining bugs

    # Rebase 6ad92e5..eadc391 onto 6ad92e5
    #
    # Commands:
    #  p, pick = use commit
    #  r, reword = use commit, but edit the commit message
    #  e, edit = use commit, but stop for amending
    #  s, squash = use commit, but meld into previous commit
    #  f, fixup = like "squash", but discard this commit's log message
    #
    # If you remove a line here THAT COMMIT WILL BE LOST.
    # However, if you remove everything, the rebase will be aborted.
    #

To achieve what we want, we will make the following changes to it::

    r 13d7934 First implementation
    pick 2dec1ac Fix a few bugs + disable
    f a815645 Modify it so that it works
    f eadc391 Fix some remaining bugs

This means that (i) we want to edit the commit message for ``13d7934``, and
(ii) collapse the last three commits into one. Now we save and quit the
editor.

Git will then immediately bring up an editor for editing the commit message.
After revising it, we get the output::

    [detached HEAD 721fc64] FOO: First implementation
     2 files changed, 199 insertions(+), 66 deletions(-)
    [detached HEAD 0f22701] Fix a few bugs + disable
     1 files changed, 79 insertions(+), 61 deletions(-)
    Successfully rebased and updated refs/heads/my-feature-branch.

and the history looks now like this::

     0f22701 Fix a few bugs + disable
     721fc64 ENH: Sophisticated feature
     6ad92e5 * masked is now an instance of a new object, MaskedConstant

If it went wrong, recovery is again possible as explained :ref:`above
<recovering-from-mess-up>`.

Fetching a pull request
^^^^^^^^^^^^^^^^^^^^^^^

To fetch a pull request on the main repository to your local working
directory as a new branch, just do::

 git fetch upstream pull/<pull request number>/head:<local-branch>

As an example, to pull the realtime pull request which has a url
``https://github.com/mne-tools/mne-python/pull/615/``, do::

 git fetch upstream pull/615/head:realtime

If you want to fetch a pull request to your own fork, replace
``upstream`` with ``origin``. That's it!

Adding example to example gallery
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Add the example to the correct subfolder in the ``examples/`` directory and
prefix the file with ``plot_``. To make sure that the example renders correctly,
run ``make html`` in the ``doc/`` folder

Editing \*.rst files
^^^^^^^^^^^^^^^^^^^^

These are reStructuredText files. Consult the Sphinx documentation to learn
more about editing them.

Troubleshooting
---------------

Listed below are miscellaneous issues that you might face:

Missing files in examples or unit tests
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

If the unit tests fail due to missing files, you may need to run
`mne-scripts`_ on the sample dataset. Go to ``bash`` if you are using some
other shell. Then, execute all three shell scripts in the
``sample-data/`` directory within ``mne-scripts/``.

Cannot import class from a new \*.py file
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

You need to update the corresponding ``__init__.py`` file and then
restart the ipython kernel.

.. include:: links.inc
