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Development workflow

You already have your own forked copy of the matplotlib repository, by following Making your own copy (fork) of matplotlib, Set up your fork, and you have configured git by following Configure git.

Workflow summary

  • Keep your master branch clean of edits that have not been merged to the main matplotlib development repo. Your master then will follow the main matplotlib repository.
  • Start a new feature branch for each set of edits that you do.
  • If you can avoid it, try not to merge other branches into your feature branch while you are working.
  • Ask for review!

This way of working really helps to keep work well organized, and in keeping history as clear as possible.

See — for example — linux git workflow.

Making a new feature branch

git checkout -b my-new-feature master

This will create and immediately check out a feature branch based on master. To create a feature branch based on a maintenance branch, use:

git fetch origin
git checkout -b my-new-feature origin/v1.0.x

Generally, you will want to keep this also on your public github fork of matplotlib. 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

You will need to use this exact command, rather than simply git push every time you want to push changes on your feature branch to your github repo. However, in git >1.7 you can set up a link by using the --set-upstream option:

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

and then next time you need to push changes to your branch a simple git push will suffice. Note that git push pushes out all branches that are linked to a remote branch.

The editing workflow

Overview

# hack hack
git add my_new_file
git commit -am 'NF - some message'
git push

In more detail

  1. Make some changes

  2. 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")
  3. Check what the actual changes are with git diff (git diff).

  4. Add any new files to version control git add new_file_name (see git add).

  5. To commit all modified files into the local copy of your repo,, do git commit -am 'A commit message'. Note the -am options to commit. The m flag just signals that you’re going to type a message on the command line. The a flag — you can just take on faith — or see why the -a flag? — and the helpful use-case description in the tangled working copy problem. The git commit manual page might also be useful.

  6. To push the changes up to your forked repo on github, do a git push (see git push).

Asking for code review

  1. Go to your repo URL — e.g., http://github.com/your-user-name/matplotlib.

  2. Click on the Branch list button:

    ../../_images/branch_list.png
  3. Click on the Compare button for your feature branch — here my-new-feature:

    ../../_images/branch_list_compare.png
  4. If asked, select the base and comparison branch names you want to compare. Usually these will be master and my-new-feature (where that is your feature branch name).

  5. At this point you should get a nice summary of the changes. Copy the URL for this, and post it to the matplotlib mailing list, asking for review. The URL will look something like: http://github.com/your-user-name/matplotlib/compare/master...my-new-feature. There’s an example at http://github.com/matthew-brett/nipy/compare/master...find-install-data See: http://github.com/blog/612-introducing-github-compare-view for more detail.

The generated comparison, is between your feature branch my-new-feature, and the place in master from which you branched my-new-feature. In other words, you can keep updating master without interfering with the output from the comparison. More detail? Note the three dots in the URL above (master...my-new-feature) and see Two and three dots in difference specs.

It’s a good idea to consult the Pull request checklist to make sure your pull request is ready for merging.

Asking for your changes to be merged into the main repo

When you are ready to ask for the merge of your code:

  1. Go to the URL of your forked repo, say http://github.com/your-user-name/matplotlib.git.

  2. Click on the ‘Pull request’ button:

    ../../_images/pull_button.png

    Enter a message; we suggest you select only matplotlib as the recipient. The message will go to the matplotlib mailing list. Please feel free to add others from the list as you like.

  3. If the branch is to be merged into a maintenance branch on the main repo, make sure the “base branch” indicates the maintenance branch and not master. Github can not automatically determine the branch to merge into.

Staying up to date with changes in the central repository

This updates your working copy from the upstream matplotlib github repo.

Overview

# go to your master branch
git checkout master
# pull changes from github
git fetch upstream
# merge from upstream
git merge --ff-only upstream/master

In detail

We suggest that you do this only for your master branch, and leave your ‘feature’ branches unmerged, to keep their history as clean as possible. This makes code review easier:

git checkout master

Make sure you have done Linking your repository to the upstream repo.

Merge the upstream code into your current development by first pulling the upstream repo to a copy on your local machine:

git fetch upstream

then merging into your current branch:

git merge --ff-only upstream/master

The --ff-only option guarantees that if you have mistakenly committed code on your master branch, the merge fails at this point. If you were to merge upstream/master to your master, you would start to diverge from the upstream. If this command fails, see the section on accidents.

The letters ‘ff’ in --ff-only mean ‘fast forward’, which is a special case of merge where git can simply update your branch to point to the other branch and not do any actual merging of files. For master and other integration branches this is exactly what you want.

Other integration branches

Some people like to keep separate local branches corresponding to the maintenance branches on github. At the time of this writing, v1.0.x is the active maintenance branch. If you have such a local branch, treat is just as master: don’t commit on it, and before starting new branches off of it, update it from upstream:

git checkout v1.0.x
git fetch upstream
git merge --ff-only upstream/v1.0.x

But you don’t necessarily have to have such a branch. Instead, if you are preparing a bugfix that applies to the maintenance branch, fetch from upstream and base your bugfix on the remote branch:

git fetch upstream
git checkout -b my-bug-fix upstream/v1.0.x

Recovering from accidental commits on master

If you have accidentally committed changes on master and git merge --ff-only fails, don’t panic! First find out how much you have diverged:

git diff upstream/master...master

If you find that you want simply to get rid of the changes, reset your master branch to the upstream version:

git reset --hard upstream/master

As you might surmise from the words ‘reset’ and ‘hard’, this command actually causes your changes to the current branch to be lost, so think twice.

If, on the other hand, you find that you want to preserve the changes, create a feature branch for them:

git checkout -b my-important-changes

Now my-important-changes points to the branch that has your changes, and you can safely reset master as above — but make sure to reset the correct branch:

git checkout master
git reset --hard upstream/master

Deleting a branch on github

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 matplotlib into your account, as from Making your own copy (fork) of matplotlib.

Then, go to your forked repository github page, say http://github.com/your-user-name/matplotlib

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

../../_images/pull_button.png

Now all those people can do:

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

Exploring 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.