What does m5base.app_start() do?

jhfoo

I learnt a lot very quickly using uiflow, and am looking to move into their alternate custom-app mode (super cool feature btw!).

Analyzing stock boot.py:

m5base.app_start(0) is called in app mode, and app_start(2) in flow mode. What does this do exactly, and should I care?
In app mode, what is the purpose behind copying the selected app into main.py? This feels unnecessary as I need to manually select the app again with the physical buttons every time I upload my code.

robalstona

if you select and run app in app selector its file was saved as main.py. And when you reset device or shutdown and power up next time or run in app mode your prewiously selected app was running (main.py).

jhfoo

@robalstona Yes I get that. But WHY? As I mentioned earlier, this makes testing code uploads a pain.