In a recent post Fabien Potencier took a look at one method for getting metadata information from a subversion repository about the project(s) inside.
Last year, I deployed a new tool to manage symfony plugins. The first goal of this tool was to simplify the process of contributing new plugins. [...] The question I wanted to answer was quite simple: How many plugins were created per month before and after the change?
He uses a very handy option to modify the output of an "svn log" command - the "--xml" argument. This outputs the latest information (like author, date, paths and msg) for each of the log entries. This can then be thrown into a call to simple_xml_load_file and parsed down into the numbers he was looking for. He even generated a graph of the results as they coordinated with the different symfony releases.