This is one of those "develop with pleasure" little touches: how about adding a horizontal ruler in the server log every time a web application is redeployed? This would help developers to separate text from a previous deployment from text that was logged after the deployment.
Of course, a feature request from me isn't complete without a lame mock-up screenshot. This one here shows a tomcat server log. The horizontal blue line shows where the text from the last redeployment starts.
still happens several times a day. Probably not too hard to do either.