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[[wikipedia:Mercurial|Mercurial]] (sometimes referred to as {{codeline|hg}}) is the version control tool used by Octave.
[https://www.mercurial-scm.org Mercurial] (sometimes referred to as {{codeline|hg}}) is the source code management system used for Octave development.
This page contains some helpful commands to use when interacting with the GNU Octave mercurial repository.
Everybody is free to '''run, copy, distribute, study, change and improve'''<ref>https://www.gnu.org/philosophy/free-sw.en.html</ref> Octave's source code, given in the main repository at https://www.octave.org/hg/octave.  Use Mercurial to get the latest version of Octave <pre>hg clone https://www.octave.org/hg/octave</pre>
== Getting the development sources ==
{{Note|[https://tortoisehg.bitbucket.io/ 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.}}
You can retrieve the source code for Octave by issuing the command
== Creating and submitting patches (changesets) ==
<pre> hg clone http://www.octave.org/hg/octave octave </pre>
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.
Packages like image, mapping, etc. are not parts of Octave itself, but of the associated Octave Forge. These have their own repositories, a list of which can be found [http://sourceforge.net/p/octave/_list/hg?source=navbar here]. Behind each link you'll be able to browse each package's source code on sourceforge and see the command for cloning the repository, for example
# Get the latest version of Octave (or some Octave package) <pre>hg clone https://www.octave.org/hg/octave</pre> or when already cloned <pre>hg pull && hg update</pre>
# Make your changes (fix bug #42424) and save them.  '''Make sure that your changes don't introduce new bugs!'''  Thus it is recommended to [[Building | build Octave]] and to [[Tests | run Octave's test suite]] before proceeding.<br>{{Warning|Please follow the [[Contribution guidelines]] for C/C++ or Octave code files!}}
# Commit your changes <pre>hg commit</pre> Mercurial will open your default editor<ref>To set your default Mercurial editor, read https://www.mercurial-scm.org/wiki/editor .</ref> and ask you for a commit message.  Please follow the [[commit message guidelines]], e.g. <syntaxhighlight lang="text">help.m: Display relevant topics first (bug #42424)
<pre> hg clone http://hg.code.sf.net/p/octave/mapping octave-mapping </pre>
* scripts/help/help.m: Describe what you changed to display relevant topics
  first.  The maximal line width is 80 characters.</syntaxhighlight>
# Export the changes <pre>hg export -r tip -o bug42424.patch</pre> The final patch for submission will look like this {{file|bug42424.patch|<syntaxhighlight lang="diff"># 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)
for the mapping package.
* scripts/help/help.m: Describe what you changed to display relevant topics
  first.  The maximal line width is 80 characters.
== Submitting patches ==
diff -r f5c9bb5955e7 -r 68c698c4f2fd scripts/help/help.m
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
--- a/scripts/help/help.m	Tue Jun 09 14:11:13 2020 -0700
# Change the code and test that your changes do work (write tests, that's the best!).
+++ b/scripts/help/help.m	Wed Jun 10 18:08:11 2020 +0900
# Create the changeset (instructions below). 
@@ -99,7 +99,7 @@ function retval = help (name)
# Post your patch in the [https://savannah.gnu.org/patch/?group=octave Patch tracker].
     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))
 
</syntaxhighlight>}}
# Upload {{Path|bug42424.patch}} to the [https://savannah.gnu.org/bugs/?group=octave bug] or [https://savannah.gnu.org/patch/?group=octave 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 <code>public.server.org/octave</code>.
 
=== Using bookmarks ===
 
[https://www.mercurial-scm.org/wiki/Bookmarks Bookmarks] are useful for identifying a series of commits.  They are a "lightweight" solution to [https://www.mercurial-scm.org/wiki/NamedBranches named branches], which are not automatically updated for example.  To create a bookmark <code>my-gsoc</code> use
 
<syntaxhighlight lang="bash">
hg clone https://www.octave.org/hg/octave
hg bookmark my-gsoc
</syntaxhighlight>
=== Before starting ===
To make the bookmark visible in the public repository use
If you wish, you can use Mercurial's [http://mercurial.selenic.com/wiki/MqExtension MQ extension] to prepare your patches.
In that case, you need to prepare your .hgrc file to use it. If you do not have a .hgrc file, just create one in your home directory.
In Windows, this is something like "C:\Documents and Settings\your_name\Mercurial.ini"
Add the following code to that file:
<syntaxhighlight lang="bash">
 [ui]
hg push --bookmark ssh://student@public.server.org/octave
 username = Your Real Name <some@email.com>
</syntaxhighlight>
 
 [extensions]
 hgext.mq =
 hgext.pager =
 color =
 
 [pager]
 pager = LESS='FSRX' less
 attend = help, annotate, cat, diff, export, glog, log, qdiff, status, outgoing, incoming
 
 ## Colours I like
 [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
The only part that is important is the extensions. The rest is to make hg behave in a fancy way (recommended).
=== Staying up-to-date with the main repository ===
=== Creating changesets with hg ===
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:
==== Simple way ====
* Update to the latest revision.  
<pre> hg up </pre>
* Make your changes and save them. 
* Commit your code. Mercurial will ask you for a commit message, which should follow the [[commit message guidelines]].
<pre> hg ci </pre>
* 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.
<pre> hg export -r tip -o mypatch.patch </pre>
* 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!
==== Using the MQ extension ====
<syntaxhighlight lang="bash">
In the repository you can start a patch by doing 
hg pull https://www.octave.org/hg/octave   # Get latest remote "tip"
  hg qnew mychangeset
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://student@public.server.org/octave
</syntaxhighlight>
You can further edit your files... if you do, you need your patch to know about these changes. To do that execute
=== Preparing for code reviews ===
 hg qrefresh
Once you think you have all the changes that make your patch complete you can export your patch
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.
 hg qdiff > mychangeset.patch
Now you can do (at least) two things
# Create a full log of changes <pre>hg log --template=changelog --no-merges --user student-name</pre> 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:
* Apply your patch to your copy (it will differ form the repository and you will have to merge somehow...). To do it run
#* Each touched file should appear only once.
 hg qfinish tip
#* Do not mention backed-out commits.
* Forget the changes and go back to the unpatched version of the code.
# Prepare a singe patch (changeset) including all code that should be submitted for review <syntaxhighlight lang="bash">
  hg qrefresh
hg pull https://www.octave.org/hg/octave   # Get remote "tip" and "@"
 hg qpop
hg update -r @                             # Activate    bookmark "@"
 hg qfinish tip
hg merge my-gsoc                           # Merge "my-gsoc" into "@"
hg commit
hg export -r tip -o mid-term-review.patch
</syntaxhighlight> The file {{Path|mid-term-review.patch}} can uploaded to the [https://savannah.gnu.org/patch/?group=octave patch tracker]. <br/> Finally, there is a subtle difference between <code>"tip"</code>, which is a reference to the (local or remote) changeset added to the repository most recently and the bookmark <code>"@"</code> 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.
The file mychangeset.patch contains your changes.
== Example Mercurial configuration ==
== Mercurial Tips for SoC students ==
Place the following file in your home directory, e.g. {{Path|/home/username/.hgrc}}.
This section is meant to provide tips for SOCIS or GSoC students working on new Octave features.
{{File|.hgrc|<syntaxhighlight lang="ini">
[ui]
username = Your Name <your@email>
Students should publish their work as it progresses in a public repository 
[extensions]
merging regularly the main savannah repository to facilitate merging back their 
color =
code at the end of the project. 
histedit =
pager =
rebase =
strip =
Here are some useful hg commands that can be used to do this.
[pager]
pager = LESS='FSRX' less
attend = help, annotate, cat, diff, export, glog, log, outgoing, incoming
=== Getting started ===
[diff]
<!--[[File:Hg-student-start.png]]-->
showfunc = True
<ol>
<li> Clone the main Octave repository at savannah:<br>
 <code> hg clone http://www.octave.org/hg/octave </code> </li>
<li> Create a new bookmark:<br>
 <code> hg bookmark student-bookmark-name </code> </li>
<li> Make the bookmark visible in the public repo, assuming the public repo is at <code>public.server.org/octave</code><br>
 <code> hg push --bookmark ssh://student@public.server.org/octave </code> </li>
</ol>
=== Staying up-to-date with the main savannah repository ===
[color]
mode = terminfo
<!-- After working for a while, the public repo should look like the following picture. -->
## Custom colors
As the students development proceeds,
color.gray = 244
the savannah repository gets updated, too. 
color.orange = 202
To avoid having the two branches diverging too much, which can
color.lightyellow = 191
lead to conflicts when the final merge is done, students should
color.darkorange = 220
keep their public repo up-to-date with the recent changes, 
color.brightyellow = 226
the following commands can be used for this:<br/>
<ol>
<!--[[File:Hg-student-flow1.png]] <br/>-->
<li> Download new changes from the main line of development <br/>
<code> hg pull http://www.octave.org/hg/octave </code> </li>
<li> Merge the main line of development into the feature branch <br/>
<code> hg up -r student-bookmark-name </code> <br/>
<!--[[File:Hg-student-flow2.png]] <br/>-->
<code> hg merge @ </code> </li>
<li> Apply the change and publish it <br/>
<code> hg commit -m "periodic merge of default branch into my branch" </code> <br/>
<!--[[File:Hg-student-flow3.png]] <br/>-->
<code> hg push ssh://student@public.server.org/octave </code></li>
</ol>
=== Preparing for code reviews ===
status.modified = magenta bold
At the time of the mid-term or final review (or whenever the mentor requires it) students should prepare their code 
status.added = green bold
for review and possibly inclusion into the main development branch. To this end students should:
status.removed = red bold
<ol>
status.deleted = cyan bold
<li> prepare a full log of their changes, listing files that have been touched 
status.unknown = gray bold
 and including a summary of the purpose of those changes. If students have been following 
status.ignored = gray bold
 the [[Commit message guidelines]] the following command will give a good starting point<br> 
 <code> hg log --style=changelog --no-merges --user student-name </code><br>
 this message should be edited so that 
 <ol   style="list-style-type: lower-roman;">
 <li> each touched file appears only once </li>
 <li> changes that were backed out should not be mentioned <!--(like changeset "H" in the above example)--> </li>
 </ol>
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]].
<li> prepare a merge changeset including all the code that should be submitted for review
  <ol style="list-style-type: lower-roman;">
  <li> pull from the main repository<br/>
  <code>hg pull http://www.octave.org/hg/octave</code></li>
  <li> move to the top of the main line of development and merge in the feature branch<br/>
  <code>hg up -r @</code><br/>
  <code>hg merge student-bookmark-name </code><br/></li>
  <li> create a changeset, export it and send to the mentor for review, remember to use the log created above as a commit message<br/>
  <code>hg commit </code><br/>
  <code>hg export @ > mid-term-review.changeset </code><br/>
  the file mid-term-review.changeset can then be sent to the [[mailto:octave-maintainers@octave.org  mailing list]] or posted
  to the [[http://savannah.gnu.org/patch/?group=octave  patch tracker]]</li>
  </ol> </li>
</ol>
== Mercurial Tips for SoC mentors ==
## Colors for each label
log.branch = cyan
log.summary = lightyellow
log.description = lightyellow
log.bookmark = green
log.tag = darkorange
log.graph = blue
Will fill in this section after trying out the above procedure at least once with a student
## Colors for each phase
and actually pushing his changes to the main repo.
changeset.secret = blue bold
changeset.draft  = red bold
changeset.public = orange
<!---
desc.here = bold blue_background
<code>
hg pull http://student.repo.url
</code>
<code>
[bookmarks]
hg pull http://www.octave.org/hg/octave
track.current = True
</code>
<code>
[alias]
hg up -r @
glog = log --graph
</code>
top = log --graph -l
</syntaxhighlight>}}
<code>
== Footnotes ==
hg merge student_bookmark
</code>
<code>
<references/>
hg log --style=changelog --user student
</code>
-->
==External links==
== External links ==
* [http://mercurial.selenic.com/ Official website]
* https://hginit.com/ -- Mercurial tutorial
* https://www.mercurial-scm.org/wiki/Tutorial -- Mercurial tutorial
* https://www.mercurial-scm.org/wiki/QuickStart -- Mercurial quick start
* https://tortoisehg.bitbucket.io/ -- TortoiseHg is a GUI for Mercurial (Linux, macOS, MS Windows)
[[Category:Development]]
[[Category:Development]]