Bridges should put their "transport" lines in their main descriptor, not extra-info desc
Bridgedb finds it a real hassle to paw through all the extrainfo descs, and match them up and check signatures and so on, just to know what ports and capabilities a given bridge is advertising.
Here's an example transport line from an extra-info desc: transport obfs3 188.8.131.52:10872
Since the transport is a capability, rather than a statistic, I think it should go in the main descriptor, like where our or-address line goes.
Another benefit here is that clients will be able to learn what other transports their bridge supports, since they fetch and have its descriptor anyway.
The only drawback I see is that it's a bit less secret what your transports are. But I think the extrainfo descriptor is served to anybody who asks for it, so it's not a secret now anyway from people who can fetch your main descriptor.
Another option is to start putting the transport line in both places for a while, so people who parse these things (e.g. Karsten) have more time to transition. Seems better just to identify all the people who parse these things, get them to prepare for it, and then just move the transport lines.
Then in the distant future, places like bridgedb can stop needing the extrainfo descriptors too.