Mercurial

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Mercurial (sometimes referred to as hg) is the source code management system currently used to develop Octave.

Introduction to mercurial[edit]

An introduction to mercurial is completely outside the scope of this document. There are plenty of available documentation on the topic. Some recommendations are:

Contributing to Octave[edit]

The preferred method to contribute to Octave is with Mercurial changesets. Other forms of contributions (e.g., simple diff patches) are also acceptable, but they slow down the review process.

If you plan on contributing to Octave:

Getting the development sources[edit]

To clone the Octave repository:

hg clone http://www.octave.org/hg/octave octave

Octave packages like image, signal, control, etc. are not parts of Octave itself, they belong to the Octave Forge. Each package has its own repository, a list of which can be found here. You can clone them in a similar way, for example, to clone the signal package

hg clone http://hg.code.sf.net/p/octave/signal octave-signal

Mercurial configuration[edit]

You can use the following to start your hgrc

File:
[ui]
username = Your Name <your@email>

[extensions]
color =
histedit =
pager =
rebase =
strip =

[pager]
pager = LESS='FSRX' less
attend = help, annotate, cat, diff, export, glog, log, qdiff, status, outgoing, incoming

[diff]
git = True
showfunc = True

[color]
status.modified = magenta bold
status.added = green bold
status.removed = red bold
status.deleted = cyan bold
status.unknown = gray  bold
status.ignored = gray bold

[alias]
log = log --graph

Submitting patches[edit]

When you do not have push permissions to the repository (you cannot add your changes using mercurial itself) and you have a modification to the current GNU Octave code, you have to generate a patch (or changeset) so developers with permissions can include them in the code. The overview of the process is as follows

  1. Change the code and test that your changes do work (write tests, that's the best!).
  2. Create the changeset (instructions below).
  3. Post your patch in the Patch tracker.


Patch submissions is done via the bug or patch trackers. Either way, you can submit via two different methods: pull requests on attaching a changeset file.

Pull request[edit]

This is the cleaner way. You push your clone to public site, and ask on the bug tracker to pull a specific changeset from it. It makes special sense if you plan to send more patches in the future but requires to host the clone somewhere. Free mercurial repositories are available on bitbucket


Creating changesets files with hg[edit]

Simple way[edit]

  • Update to the latest revision.
 hg up 
  • Make your changes and save them.
  • Commit your code. Mercurial will ask you for a commit message, which should follow the commit message guidelines.
 hg ci 
  • Export the modifications. This creates a file (in the case of the example below, it is called mypatch.patch) that contains a description of the changes that you've made. Someone else can then apply the patch and end up with a repository that looks the same as yours.
 hg export -r tip -o mypatch.patch 
  • Save the output to a file and upload it to the patch tracker. If your patch file is larger than the upload limit, you can compress it before uploading. Please use a free format!

Mercurial Tips for SoC students[edit]

This section is meant to provide tips for SOCIS or GSoC students working on new Octave features.

Students should publish their work as it progresses in a public repository merging regularly the main savannah repository to facilitate merging back their code at the end of the project.

Here are some useful hg commands that can be used to do this.

Getting started[edit]

  1. Clone the main Octave repository at savannah:
    hg clone http://www.octave.org/hg/octave
  2. Create a new bookmark:
    hg bookmark student-bookmark-name
  3. Make the bookmark visible in the public repo, assuming the public repo is at public.server.org/octave
    hg push --bookmark ssh://student@public.server.org/octave

Staying up-to-date with the main savannah repository[edit]

As the students development proceeds, the savannah repository gets updated, too. To avoid having the two branches diverging too much, which can lead to conflicts when the final merge is done, students should keep their public repo up-to-date with the recent changes, the following commands can be used for this:

  1. Download new changes from the main line of development
    hg pull http://www.octave.org/hg/octave
  2. Merge the main line of development into the feature branch
    hg up -r student-bookmark-name
    hg merge @
  3. Apply the change and publish it
    hg commit -m "periodic merge of default branch into my branch"
    hg push ssh://student@public.server.org/octave

Preparing for code reviews[edit]

At the time of the mid-term or final review (or whenever the mentor requires it) students should prepare their code for review and possibly inclusion into the main development branch. To this end students should:

  1. prepare a full log of their changes, listing files that have been touched and including a summary of the purpose of those changes. If students have been following the Commit message guidelines the following command will give a good starting point
    hg log --style=changelog --no-merges --user student-name
    this message should be edited so that
    1. each touched file appears only once
    2. changes that were backed out should not be mentioned

    The main purpose of this log is to make it easy, not only for the main mentor, but also for other developers who have not been closely following the progress of the project to quickly understand where to look at in the code to evaluate it, but it will also be used as the commit message for the merge changeset, so it should itself comply with the Commit message guidelines.

  2. prepare a merge changeset including all the code that should be submitted for review
    1. pull from the main repository
      hg pull http://www.octave.org/hg/octave
    2. move to the top of the main line of development and merge in the feature branch
      hg up -r @
      hg merge student-bookmark-name
    3. create a changeset, export it and send to the mentor for review, remember to use the log created above as a commit message
      hg commit
      hg export @ > mid-term-review.changeset
      the file mid-term-review.changeset can then be sent to the [mailing list] or posted to the [patch tracker]

Mercurial Tips for SoC mentors[edit]

Will fill in this section after trying out the above procedure at least once with a student and actually pushing his changes to the main repo.

External links[edit]