pub fn first_difference(old: &Path, installed: &Path) -> Result<Option<String>>Expand description
What:
The first way the old tree at old is not held by the installed tree at installed, or nothing when it is held whole.
Why:
See the module description. A file is the same when its type, size and modification time are, a link when its target is;
the installed tree may hold more than the old one, because it has been in use since the exchange.
In TS you’d write (pseudocode):
firstDifference(old, installed);