I guess people experienced enough to be using a versioning system like Subversion will already know this but "chowning" all the files and folders in a working copy to www will play havoc with the versioning system. It will no longer be able to write the files and folders it needs to write.

Better to take more careful approaches if you're using versioning.

A better solution may be to temporarily change the webserver (Apache) user to your own user name.

For 10.5 (maybe others) the httpd.conf file is in...

private/etc/apache2

Simply change the: User www

to your user name. Restart Apache by turning web sharing off then on, then run the installers or whatever you need the web app to do then change the user name back.

Much simpler and cleaner solution in my opinion and less likely to cause other problems.