httppeer: handle error response from client reactor With this in place, we're now seeing useful errors when running tests with the new wire protocol enabled! Differential Revision: https://phab.mercurial-scm.org/D3332

wireproto: add media type to version 2 capabilities response This is useful to advertise because servers reject unsupported media types. A client may wish to speak multiple media types and choose the one the server supports. I doubt we'll ever use multiple media types or negotiation in core. But during the course of developing this protocol, I may end up making extensions that backport and forward port protocol support as needed to support Mercurial deploys in the wild. e.g. I may deploy support for an older protocol on a server so old clients can continue using it. It's worth pursuing changing the SSH protocol's upgrade mechanism to support multiple media types as well... Differential Revision: https://phab.mercurial-scm.org/D3299

debugcommands: use command executor for invoking commands Now that all peers support the command executor interface, we can use it in place of peer._call() (which isn't part of the public API). Tests changed because we are now returning the decoded response instead of the raw bytes. The raw bytes over the wire are already logged. So we're not losing any test coverage. In fact, we're adding test coverage because we're testing decoding of those command responses as well. Differential Revision: https://phab.mercurial-scm.org/D3298

httppeer: implement command executor for version 2 peer Now that we have a new API for issuing commands which is compatible with wire protocol version 2, we can start using it with wire protocol version 2. This commit replaces our hacky implementation of _call() with something a bit more robust based on the new command executor interface. We now have proper support for issuing multiple commands per HTTP request. Each HTTP request maintains its own client reactor. The implementation is similar to the one in the legacy wire protocol. We use a ThreadPoolExecutor for spinning up a thread to read the HTTP response in the background. This allows responses to resolve in any order. While not implemented on the server yet, a client could use concurrent.futures.as_completed() with a collection of futures and handle responses as they arrive from the server. The return value from issued commands is still a simple list of raw or decoded CBOR data. This is still super hacky. We will want a rich data type for representing command responses. But at least this commit gets us one step closer to a proper peer implementation. Differential Revision: https://phab.mercurial-scm.org/D3297