Transition path for renamed/refined settings?

[oscargus]

Maybe I missed it in the docs, but is there a good way to update config names. Say that I have a config foo that I in my next version would like to duplicate for finer settings to foo_a and foo_b. Is there a good way to handle this so that users that have set foo can still use it and do not have to change it/get error messages?

An alternative is to keep foo and add foo_b. Basically, some way to transition from "old" configs to "new".

[epage]

I am no aware of a way to support this today. The big challenge with it is that I assume users would want the fallback to occur at each layer of the config so that foo in the current directory overrides foo_a in the user home, rather than foo_a from user home just because foo_a is the newer name.