Making a new feature branch¶

To update your master branch, use:

git fetch upstream
git merge upstream/master --ff-only

To create a new branch and check it out, use:

git checkout -b my-new-feature upstream/master

Generally, you will want to keep this branch also on your public github fork of NumPy. 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 your own github repo.

The editing workflow¶

# hack hack
git add my_new_file
git commit -am 'ENH: some message'

# push the branch to your own Github repo
git push

ENH: add functionality X to numpy.<submodule>.

The first line of the commit message starts with a capitalized acronym
(options listed below) indicating what type of commit this is.  Then a blank
line, then more text if needed.  Lines shouldn't be longer than 80
characters.  If the commit is related to a ticket, indicate that with
"See #3456", "See ticket 3456", "Closes #3456" or similar.

API: an (incompatible) API change
BLD: change related to building numpy
BUG: bug fix
DEP: deprecate something, or remove a deprecated object
DEV: development tool or utility
DOC: documentation
ENH: enhancement
MAINT: maintenance commit (refactoring, typos, etc.)
REV: revert an earlier commit
STY: style fix (whitespace, PEP8)
TST: addition or modification of tests
REL: related to releasing numpy

Rebasing on master¶

This updates your feature branch with changes from the upstream NumPy github repo. If you do not absolutely need to do this, try to avoid doing it, except perhaps when you are finished.

First, it can be useful to update your master branch:

# go to the master branch
git checkout master
# pull changes from github
git fetch upstream
# update the master branch
git rebase upstream/master
# push it to your Github repo
git push

Then, the feature branch:

# go to the feature branch
git checkout my-new-feature
# make a backup in case you mess up
git branch tmp my-new-feature
# rebase on master
git rebase master

If you have made changes to files that have changed also upstream, this may generate merge conflicts that you need to resolve. Finally, remove the backup branch once the rebase succeeded:

git branch -D tmp

git rebase --abort

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

# look at the reflog of the branch
git reflog show my-feature-branch

8630830 my-feature-branch@{0}: commit: BUG: io: close file handles immediately
278dd2a my-feature-branch@{1}: rebase finished: refs/heads/my-feature-branch onto 11ee694744f2552d
26aa21a my-feature-branch@{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 my-feature-branch@{2}

Asking for your changes to be merged with the main repo¶

When you feel your work is finished, you can ask for code review, or directly file a pull request.

Pushing changes to the main repo¶

When you have a set of “ready” changes in a feature branch ready for Numpy’s master or maintenance/1.5.x branches, you can push them to upstream as follows:

1. First, merge or rebase on the target branch.

   1. Only a few commits: prefer rebasing:

      git fetch upstream
      git rebase upstream/master

      See above.

   2. Many related commits: consider creating a merge commit:

      git fetch upstream
      git merge --no-ff upstream/master

2. Check that what you are going to push looks sensible:

   git log -p upstream/master..
   git log --oneline --graph

3. Push to upstream:

   git push upstream my-feature-branch:master

Rewriting commit history¶

There’s an embarassing 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 master 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 above.

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

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

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

Now all those people can do:

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