Mercurial

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

Contributing to Octave

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:

• See other Contribution guidelines
• Always include commit messages in changesets. Please follow the Octave commit message guidelines
• Follow the style guides for both Octave and C++ languages.

Submitting patches

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 or attaching a changeset file.

Creating changesets (patches)

1. Get the latest revision of Octave (or some Octave package)

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

   or when already cloned

   hg pull && hg update

2. Make your changes (fix the bug) and save them.
3. Commit your changes

   hg commit

   Mercurial will open your default editor and ask you for a commit message. Please follow the commit message guidelines, e.g.

   help.m: Display relevant topics first (bug #42424)
   
   * scripts/help/help.m: Describe how to display relevant topics first.
   

4. Export the changes

   hg export -r tip -o bug42424.patch

   The final patch for submission will look like this
5. Upload bug42424.patch to the bug or 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

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

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

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

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

Example Mercurial configuration

Place the following file in your home directory, e.g. /home/username/.hgrc.

File: .hgrc

[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, outgoing, incoming

[diff]
showfunc = True

[color]
mode = terminfo

## Custom colors
color.gray = 244
color.orange = 202
color.lightyellow = 191
color.darkorange = 220
color.brightyellow = 226

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

## Colours for each label
log.branch = cyan
log.summary = lightyellow
log.description = lightyellow
log.bookmark = green
log.tag = darkorange
log.graph = blue

## Colors for each phase
changeset.secret = blue bold
changeset.draft  = red bold
changeset.public = orange

desc.here = bold blue_background

[bookmarks]
track.current = True

[alias]
glog = log --graph
top = log --graph -l

External links

• https://hginit.com/ -- Mercurial tutorial
• https://www.mercurial-scm.org/wiki/Tutorial -- Mercurial tutorial
• https://www.mercurial-scm.org/wiki/QuickStart -- Mercurial quick start