Open main menu

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

Everybody is free to run, copy, distribute, study, change and improve[1] Octave's source code, given in the main repository at Use Mercurial to get the latest version of Octave

hg clone
Info icon.svg
TortoiseHg is a GUI for Mercurial and it is especially recommended for users doing their first steps with source code management systems. Linux, macOS, and MS Windows are supported.

Creating and submitting patches (changesets)Edit

If you want to share your modifications, for example to fix a nasty bug #42424, you cannot just submit your changes to Octave's main repository. You have to generate a patch (or changeset) so other Octave developers can include them into Octave's source code.

  1. Get the latest version of Octave (or some Octave package)
    hg clone
    or when already cloned
    hg pull && hg update
  2. Make your changes (fix bug #42424) and save them. Make sure that your changes don't introduce new bugs! Thus it is recommended to build Octave and to run Octave's test suite before proceeding.
    Please follow the Contribution guidelines for C/C++ or Octave code files!
  3. Commit your changes
    hg commit
    Mercurial will open your default editor[2] 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 what you changed to display relevant topics
      first.  The maximal line width is 80 characters.
  4. Export the changes
    hg export -r tip -o bug42424.patch
    The final patch for submission will look like this
    File: bug42424.patch
    # HG changeset patch
    # User Awesome Hacker <>
    # Date 1591780091 -32400
    #      Wed Jun 10 18:08:11 2020 +0100
    # Node ID 68c698c4f2fd98bf2d48234bd1da99e91763114f
    # Parent  f5c9bb5955e7c9fddef5c3c3f115201e11b43b79
    help.m: Display relevant topics first (bug #42424)
    * scripts/help/help.m: Describe what you changed to display relevant topics
      first.  The maximal line width is 80 characters.
    diff -r f5c9bb5955e7 -r 68c698c4f2fd scripts/help/help.m
    --- a/scripts/help/help.m	Tue Jun 09 14:11:13 2020 -0700
    +++ b/scripts/help/help.m	Wed Jun 10 18:08:11 2020 +0900
    @@ -99,7 +99,7 @@ function retval = help (name)
         ## Get help text
    -    [text, format] = get_help_text (name);
    +    [text, format] = get_better_help_text (name);
         ## Take action depending on help text format
         switch (lower (format))
  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 studentsEdit

This section is meant to provide tips for Summer of Code students working on new Octave features.

Students should publish their work as it progresses in a public repository. In this section we use for example

Using bookmarksEdit

Bookmarks are useful for identifying a series of commits. They are a "lightweight" solution to named branches, which are not automatically updated for example. To create a bookmark my-gsoc use

hg clone
hg bookmark my-gsoc

To make the bookmark visible in the public repository use

hg push --bookmark ssh://

Staying up-to-date with the main repositoryEdit

Octave development does not stand still while the students development proceeds. Octave's main repository gets updated, too. The following commands can be used to get these updated to the students clone of the main repository:

hg pull   # Get latest remote "tip"
hg update -r my-gsoc                       # Activate bookmark "my-gsoc"
hg merge tip                               # Merge  "tip" into "my-gsoc"
hg commit -m "maint: merge default to my-gsoc"
hg push ssh://

Preparing for code reviewsEdit

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 repository.

  1. Create a full log of changes
    hg log --template=changelog --no-merges --user student-name
    If students have been following the Commit message guidelines the output is a good starting point for the commit message in the next step. Some manual post-processing might be necessary:
    • Each touched file should appear only once.
    • Do not mention backed-out commits.
  2. Prepare a singe patch (changeset) including all code that should be submitted for review
    hg pull   # Get remote "tip" and "@"
    hg update -r @                             # Activate    bookmark "@"
    hg merge my-gsoc                           # Merge "my-gsoc" into "@"
    hg commit
    hg export -r tip -o mid-term-review.patch
    The file mid-term-review.patch can uploaded to the patch tracker.
    Finally, there is a subtle difference between "tip", which is a reference to the (local or remote) changeset added to the repository most recently and the bookmark "@" used by the Octave developers to point to the latest remote changeset. Often both refer to the very same changeset and they can used interchangeably.

Example Mercurial configurationEdit

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

File: .hgrc
username = Your Name <your@email>

color =
histedit =
pager =
rebase =
strip =

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

showfunc = True

mode = terminfo

## Custom colors
color.gray = 244 = 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

## Colors 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 = bold blue_background

track.current = True

glog = log --graph
top = log --graph -l


External linksEdit