Request to support new roles in the relation editor's member sort routine.

[pelderson@…]

(Related to ticket #19403 but it's a different request)

Five new roles have been approved for route relations. See ​​osmwiki:Proposed_features/Recreational_route_relation_roles
The roles are: alternative, approach, excursion, connection, main.
No role is the same as main for data users, but the explicit value main is now an approved value.

JOSM sorting in the relation editor does not yet handle the new roles when they are set on way members
Roles forward and backward on ways, as defined for routes where the directions differ at some locations, are handled as intended by the sorting routine.
Other roles are currently ignored. The request is to sort the ways for each role separately (forward and backward are sorted as main). So main, foward and backward are sorted like it is now; all alternative ways are sorted separately and kept together; all excursions idem; etc. Let's call it: grouped sorting. This could be generic: the sort does not have to check for specific roles other than forward/backward, it can simply group all members with the same role together, alphabetically.

Multiple roles on one way are currently not approved. Some mappers have suggested a semicolon-separated list of roles could be assigned to a way, but no consensus has been reached about that. However, it is the only way to register a way which serves as, say, an approach, and at the same time has a backward or forward role to assign it to a direction. The way would then be expected to be sorted into the approach group and presented there according to the forward role.