For instructions on the use of
1. diffcol (the diffcol task), see
http://internal.greenstone.org/wiki/About_Nightly_Crons#Diffcol
http://internal.greenstone.org/wiki/About_Nightly_Crons#Setting_up_and_running_diffcol_on_Windows
http://internal.greenstone.org/wiki/About_Nightly_Crons#Setting_up_and_running_diffcol_on_the_Mac

2. For the gen-model-colls.sh script, see
http://internal.greenstone.org/wiki/About_Nightly_Crons#Automatically_adding_new_or_rebuilding_existing_model-collections