add more GTFS-related & HAFAS-related libraries

[derhuerst]

Make an individual pull request for each suggestion.

Sorry, didn't follow this rule. Will split it into separate commits/PRs if you want.

Link additions should be added to the relevant category in alphabetically order.

That is not the case currently, wasn't sure wether to obey this rule.

[barbeau]

Thanks @derhuerst for adding these to the list! For alphabetical order - this was added recently, and right now only the libraries section really followed it. I tweaked some formatting and will merge.

Also - are you or others currently using GTFS-RT DIFFERENTIAL -> FULL converter (https://github.com/derhuerst/gtfs-rt-differential-to-full-dataset) in production? If so, what feeds are you using it on?

[derhuerst]

Also - are you or others currently using GTFS-RT DIFFERENTIAL -> FULL converter (https://github.com/derhuerst/gtfs-rt-differential-to-full-dataset) in production? If so, what feeds are you using it on?

No, not yet. Also, keep in mind that, strictly speaking, it is not fully DIFFERENTIAL-compatible, because the DIFFERENTIAL spec is still a draft and because I didn't implement all cases yet. See also derhuerst/gtfs-rt-differential-to-full-dataset#2 and see derhuerst/gtfs-rt-differential-to-full-dataset#1. I plan to match the current draft eventually, but contributions are welcome!

[barbeau]

Also, keep in mind that, strictly speaking, it is not fully DIFFERENTIAL-compatible, because the DIFFERENTIAL spec is still a draft

Yes, that's why I asked 😄. I have an open issue here to try and finalize DIFFERENTIAL as part of the GTFS-RT spec:
google/transit#84

There aren't many implementations today. Please feel free to weigh in there as you get more experience implementing/using it!