Extra exit numbers are discarded

[1ec5]

This route takes exit 1A by way of a collector-distributor lane shared between exits 1A and 1B. However, OSRM Text Instructions ends up saying “take exit 1B” and never says “take exit 1A”.

The highway=motorway_link way shared between the two exits is correctly tagged junction:ref=1B;1A, but OSRM Text Instructions discards all but the first exit number, saying only 1B. Until Project-OSRM/osrm-backend#4222 and Project-OSRM/osrm-backend#4295 are resolved, OSRM Text Instructions should include all the available exit numbers. If an exit number like 30A;30B;30C would be too verbose, perhaps we can perform an abbreviation like “exit 30A–C” (which is often how such exits are signposted).

/ref Project-OSRM/osrm-backend#4222 (comment)
/cc @freenerd

[1ec5]

• 7 ways tagged with multiple values in junction:ref
• 753 highway=motorway_junction nodes tagged with multiple values in ref

Note that many ref tags indicate multiple values using - instead of ; (example), so they’re currently unaffected by this issue but would be affected as soon as someone retags the exit to use junction:ref.

[1ec5]

@bsudekum pointed out that we also trim off all but the first destination in a ramp instruction. In many cases it makes sense to do so, for brevity's sake. Rather than include the full list of destinations, which could be a dozen words long, I think we should prioritize Project-OSRM/osrm-backend#4222, which would optimize the instruction to only include the relevant destination in cases where the choice makes a significant difference.