color: avoid shadowing a variable inside a list comprehension

memory: avoid shadowing variables inside a list comprehension

shelve: move shelve-finishing logic to a separate function With future obs-based shelve, finishing shelve will be different from just aborting a transaction and I would like to keep both variants of this functionality in a separate function.

shelve: move unknown files handling to a separate function This change has nothing to do with future obsshelve introduction, it is done just for readability purposes.