It may seem silly to most of you but not very clear. If in the synaptic repository list one has used testing in Jessie by now the system has converted fully (99.99%) to Debian 9 Stretch. Right?
When the official release comes and Stretch becomes stable, will the system upgrade automatically to what now is unstable? If one wishes to remain in Stretch stable what is the adjustment that needs to be made before hand? Switch anywhere that says Jessie to Stretch and anywhere it says testing to main/stable ? Will there be a difference between jessie/testing and stretch/main ? Please be specific what one needs to write to synaptic repository list (I suppose that alters the apt.config file) if one wishes to remain to stretch stable. And what happens if you are in stretch and list testing, does it really go to sid? That simple? If you are listing jessie and testing it stays in stretch? Katrin