Git is another offender here. When they decided to switch to the smart protocol by default, the Git people decided that the way to probe for server support was

Git is another offender here. When they decided to switch to the smart protocol by default, the Git people decided that the way to probe for server support was to append a query parameter to the resource. Extra parameters are ignored by default on Apache (or something), and it worked on whatever the committer tested it on, so that became how Git worked. Whereas the parameter is part of the smart protocol, any server that supports it will give a response in line with what the smart protocol dictates, and the client will proceed with having recognized a server with smart protocol support. Dumb servers who ignore extra query parameters and respond with the kind of thing that dumb servers respond with will be treated as having no support for the smart protocol, and the Git client will allow the connection to fall back to the older protocol. Meanwhile, you can have a server that only supports the dumb protocol but doesn't ignore extra parameters, and so the switch in the client defaults just broke all transactions with those servers. The Git developers either didn't test it or didn't care. And something that makes the whole thing particularly silly/frustrating is that HTTP already has ways to do content negotiation which could have been used in lieu of the boneheaded scheme they came up with.