[Refactoring] making string duplication more obvious

Split the path strings, replacing all "/" separators with the </>
operator.
[Refactoring] Replace string literals with constants
[Refactoring] more string literals to constants.

Refactoring any further will make this too specific (the two rules have
duplication still), and harder to extend. Some more copy-paste-modify
before doing more extractions, otherwise the abstractions become too
narrow.