Software or Configuration: Locking files when someone edits them

[micdhack]

I need to ask if there is a configuration or a software that can lock files when edited and free them when work is done by the user. I need this for group development of a project.

[rapiscan]

I recommend a version control system like SVN:
http://subversion.tigris.org/

This allows multiple people to check out files from a repository and they can all edit the files at the same time. If two people edited the same file, you can merge the changes.

You can install subversion like so:
sudo apt-get install subversion

[micdhack]

subversion is good for version control but since the site will have its internal version control in future(created by us) i want something simpler like locking a file when used from an utility(nano, proftpd) and unlock it after a certain amount of time. I don't know if this is possible to be achieved.