Mercurial

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

Creating and submitting patches (changesets)

Everybody is free to obtain, built, and modify Octave's source code, given in the main repository at https://www.octave.org/hg/octave. 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 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 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 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 <awesome@hacker.com>
   # 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)
        endif
    
        ## 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 students

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 public.server.org/octave.

Using bookmarks

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 https://www.octave.org/hg/octave </code>
hg bookmark my-gsoc

To make the bookmark visible in the public repository use

hg push --bookmark ssh://student@public.server.org/octave

Staying up-to-date with the main 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 https://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 https://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

## 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

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