We need a way to control the environment in Pegasus Lite. This could be used to set up the extra environment needed for some transfer clients.

It needs be able to handle dynamic cases based on the node the jobs starts on, which implies sourcing a script.

The script needs to be transferred with transfer_input_files as it is needed to setup the environment for other transfers. This is similar to how we transfer credentials.

One approach would be env var in the site catalog (PEGASUS_LITE_ENV_SCRIPT?), which is then transferred to the site, and if Pegasus Lite sees the script, sources it early on in the process.