GTFS-RT REPLACEMENT contains all scheduled stops?

For replacement trips, we would like to have a complete list of stops:

- stops that were initially scheduled:
- skipped
- not skipped
- additional stops

So the question is: Can we rely on the producer to output *all* stops from the scheduled trip or only those that still remain in the replacement trip?

The Reference says:

> The **complete** journey of the replacement trip must be specified via StopTimeUpdates

The best practice say:

> If the trip runs on a modified schedule or stops, but can be associated to an original scheduled trip in the GTFS static, use REPLACEMENT and specify the **full** list of stop times for the modified trip.

However, neither "**complete**" nor "**full**" are defined in a way that I can derive if the consumer can expect *every* stop from the scheduled trip (even those that are skipped now) or if we have to "diff" the new stop sequence with the scheduled stop sequence on the consumer side.

I think it would make sense to clarify the reference in one of those directions, so it's clear:
- either to make it obvious that "**full**" / "**complete**" refer to *all* stops, including skipped ones (so the consumer can expect them to be contained in GTFS RT)
- or to make it obvious that "**full**" / "**complete**" refer to the stops that are actually served by the replacement trip and if a consumer wants to display scheduled stops that are skipped now as skipped, then the consumer has to figure this out

I have no opinion on what's better here but I would like to clarify the standard in the direction that most producers do right now already anyway.

So the questions are:
- Did I miss something in the standard and it is already specified somewhere?
- If it's not specified: how do producers behave with regards to skipped stops once contained in the scheduled trip?

Start by reviewing the GTFS-RT Reference and best-practice wording quoted in the issue. Compare those requirements with producer behavior for skipped stops, then determine whether “complete” and “full” include every scheduled stop or only stops served by the replacement trip. Done means the standard’s expectation and the producer behavior are documented clearly.

Written by the indexing model from the issue text.