Editing Commit message guidelines

Our commit messages for Mercurial get automatically distilled into GNU Changelog entries. The GNU coding standards have [http://www.gnu.org/prep/standards/html_node/Style-of-Change-Logs.html some guidelines] for how to write Changelogs, and since Octave is a GNU project, we try to produce Changelogs in this style. However, certain things have to be adapted because the style in there is primarily for C sources, and because we are producing them from Mercurial commit messages.

You can see how [[Mercurial]] will produce the Changelog-style output with the following command:

  hg log --style changelog

*Note that this command will print all changelogs to the screen, currently including all changelogs back to 2008 and approaching 200,0000 lines of text. You may use the followig command for a paged output:

  hg log --style changelog | less

*Alternatively, you may save the changlogs to a text file. This will permit viewing and searching in a text editor for use in preparing your own commit messages:

  hg log --style changelog >> octave_changelogs.log


== Guidelines ==

General structure of a commit message:

:: '''One-line description'''
:: ''Empty line''
:: '''Body of the commit message'''

=== One-line description === 

The commit message should start with a brief one-line description of what the
commit does. Keep it short, no longer than 80 characters. If you are working
on a bug or applying a patch, this one-line explanation should mention the bug
or patch number at the end like so: {{codeline|... (bug #12345)}}. Do not end
the first line with a period (full stop).

If your change only touches one file, then the name of that file can be the
prefix of the one-line description. If it's a C++ or C file, the function or
class that is being modified should be included in the parenthetical remark,
as in the full body of the commit message.

In addition, there are a few prefixes for certain types of commits:

* maint: for reorganisation of the sources that do not change the source. Regular merge commits are a prominent example.
* doc: for changes to the documentation.
* build: for changes to the build system, for example autoconf or automake files.

If your change is small and only touches one file, then the one-line
description may serve as the entire commit message.

=== Body of the commit message ===

If there is more than one file touched in different ways and the one-line
description isn't enough to describe all changes, the commit message needs
a full-body description.

Individual files you touched get their changes separately enumerated. If
there a particular C or C++ function you changed, the general format is

<pre>
* file.cc (class1::function1): Make change foo. 
(class2::function2): Make change bar.
</pre>

Note the newline for describing the change to a different function. General
GNU style guidelines can be followed here, so that similar changes to
different files can be grouped.

For m-script and Fortran sources, the function name can be omitted if
the m-script only contains one file. For changes outside of functions
or classes, of course the parenthetical (function) or (class::function)
specifiers can also be omitted.

=== Wording ===

Please write "New function" instead of "Added function" or "Return retval"
instead of "Changed to return retval".

Never write "Fixed bug" or similar. That doesn't add any specific
information about what was changed.

The commit message should describe what was changed, not why it was changed.
Any explanation for why a change is needed should appear as comments in the
code, particularly if there is something that might not be obvious to someone
reading it later.


== Examples ==

<pre>
look for methods before constructors

* symtab.cc (symbol_table::fcn_info::fcn_info_rep::find):
Look for class methods before constructors, contrary to Matlab
documentation.
* test/ctor-vs-method: New directory of test classes.
* test/test_ctor_vs_method.m: New file.
* test/Makefile.am: Include ctor-vs-method/module.mk.
(FCN_FILES): Include test_ctor_vs_method.m in the list.
</pre>

<pre>
allow abbreviations for optimset and optimget (bug #38999)

* optimset.m, optimget.m: Handle abbreviated keys and warn for
 ambiguous abbreviations. New tests.
</pre>

<pre>
add format option to ticklabel (bug #34906)

* graphics.cc: add new functions to support different input arguments to
  xyzticklabel. Add tests.
* graphics.in.h: define set_xyzticklabel as external function
</pre>

<pre>
tag symbols in indexed assignments as variables (bug #39240)

* pt-arg-list.cc (tree_argument_list::variable_names): Also return the
  symbol names from index expressions.
* parser.tst: New test.
</pre>

=== One line commit examples ===

This examples are the rare cases where only one file is modified and the
change is simple enough:

<pre>maint: merge away accidental head.</pre>
<pre>maint: Strip trailing whitespace from source files.</pre>
<pre>maint: Update gnulib to latest changes.</pre>
<pre>maint: Periodic merge of stable to default.</pre>
<pre>doc: grammarcheck documentation for 4.2 release.</pre>
<pre>pkg.m4: update to lastest version as released with pkg-config 0.29 (bug #48775)</pre>
<pre>uigetfile.m: allow path names as input arg (bug #48828)</pre>


[[Category:Development]]