Before going any further, take a look at Branch and releases to understand what we mean when talking about trunk, branches and releases.
# working on trunk
$ svn checkout http://piwigo.org/svn/trunk
$ cd trunk
$ vi feed.php
$ vi notification.php
$ svndiff feed.php notification.php
$ svn commit -m"add new informations in RSS notification feed" feed.php notification.php
# working on branch 1.5
$ svn checkout http://piwigo.org/svn/branches/1.5
$ vi include/functions_html.inc.php
$ svn commit -m"bug 256 fixed: wrong tags for HTML menus" include/functions_html.inc.php
Each commit log must have a distinct paragraph for each modification done. Two paragraphs are separated with an empty line. Each kind of modification must be easy to understand just by reading the log.
The following example shows a commit log with several kind of modification. Of course, you won't ever have as many modifications in a single commit, it's just an example. Thanks to be rigorous enough for “bug XXX fixed:”, “merge -r?:? from ? into ? (bug ? fixed)”, “feature XXX added:”.
bug 205 fixed: advise to perform maintenance actions at the end of upgrade
feature 147 added: add a menu to manage manually create_listing_file.php
on remote sites
new: "quick start" section in Administration>General>Instructions
improvement: long localized messages are in HTML files instead of $lang
array. This is the case of admin/help and about pages.