Make socket I/O non-blocking and add optional timeouts.
Users may now set `GIT_OPT_SET_SERVER_CONNECT_TIMEOUT` to set a shorter
connection timeout. (The connect timeout cannot be longer than the
operating system default.) Users may also now configure the socket read
and write timeouts with `GIT_OPT_SET_SERVER_TIMEOUT`.
By default, connects still timeout based on the operating system
defaults (typically 75 seconds) and socket read and writes block.
Add a test against our custom testing git server that ensures that we
can timeout reads against a slow server.
`git_stream_register_tls` is now deprecated; mark it in an if guard with
the deprecation.
This should not be included in `deprecated.h` since it is an uncommonly
used `sys` header file.
Since we now always build the library with cdecl calling conventions,
our callbacks should be decorated as such so that users will not be able
to provide callbacks defined with other calling conventions.
The `GIT_CALLBACK` macro will inject the `__cdecl` attribute as
appropriate.
Accept an enum (`git_stream_t`) during custom stream registration that
indicates whether the registration structure should be used for standard
(non-TLS) streams or TLS streams.
Update the new stream registration API to be `git_stream_register`
which takes a registration structure and a TLS boolean. This allows
callers to register non-TLS streams as well as TLS streams.
Provide `git_stream_register_tls` that takes just the init callback for
backward compatibliity.
Introduce `git_tls_stream_wrap` which will take an existing `stream`
with an already connected socket and begin speaking TLS on top of it.
This is useful if you've built a connection to a proxy server and you
wish to begin CONNECT over it to tunnel a TLS connection.
Also update the pluggable TLS stream layer so that it can accept a
registration structure that provides an `init` and `wrap` function,
instead of a single initialization function.
If the stream claims to support this feature, we can let the transport
set the proxy.
We also set HTTPPROXYTUNNEL option so curl can create a tunnel through
the proxy which lets us create our own TLS session (if needed).
We currently have gitno for talking over TCP, but this needs to know
about both plaintext and OpenSSL connections and the code has gotten
somewhat messy with ifdefs determining which version of the function
should be called.
In order to clean this up and abstract away the details of sending over
the different types of streams, we can instead use an interface and
stack stream implementations.
We may not be able to use the stackability with all streams, but we
are definitely be able to use the abstraction which is currently spread
between different bits of gitno.
