I would like a job to build my projects, but build a different ant target
depending on how it was triggered. For example I would like to have the normal
build run off Polling the SCM. This does an svn update, builds the project and
runs some unit tests. Every night at 2am I would like to do all the above, but
delete my build folder first so I get a totally clean build and also run some
integration tests.

If I could somehow tell ant to run a different target for the different build
triggers, or set an environment variable that I could look at inside the ant
build, or...

Is this currently possible?