+ [<qualifier>/...]<nickname-path-spec>
+where <qualifier>/ is one of
+ [<email>]@[<domain.name>/
+ Only branches matching the specified email local part
+ or domain name match
+ [<date-spec>/]
+ A prefix of the ISO8601 date spec, stopping
+ just after a numeric component (or at the end)
+ [<approx-date-containing-~>/]
+ Intepreted by date -d after ~s have been replaced by
+ spaces. When we come to select, take the branch
+ nearest that date rather than the most recent
+