Function billable_csv 

pub fn billable_csv(
    all: &[Entry],
    project: &Project,
    from: Date,
    to: Date,
    default_rate: f64,
    french: bool,
    words: [&str; 5],
) -> String

A project’s billable time from from to to (both included), as a spreadsheet reads it: what was done, how many hours, at what rate, for how much, one line per task (or note), then the total. Nothing else: a full invoice is the invoice’s (invoice.rs). In French, ; between fields and a decimal comma, as French spreadsheets expect; else , and a point.