Fixes paths thing

[ranjitjhala]

Adds @nilehmann 's deserialize thing

fixes #918

[ranjitjhala]

Um ... ok for some odd reason the neg tests are all failing ? Any clue?

[ranjitjhala]

@nilehmann ?

[nilehmann]

calling split(",") on the empty springs results in a vec![""], so the default config always skips everything. To account for possible whitespace:

        let paths = String::deserialize(deserializer)?
            .split(",")
            .map(str::trim)
            .filter(|s| !s.is_empty())
            .map(PathBuf::from)
            .collect();

but also maybe better to make it an Option<Paths> to be more explicit