fix: No HTTP_PROXY when connecting to Docker socket

CLIv2 sets up a global proxy where all traffic from the typescript
modules / CLI parts are routed through a Go proxy. This is an issue for
the Docker modem where we want to connect to Docker's socket directly,
as the proxy alters the behaviour of the calls. Because traffic to a
socket does not need a `host` or `port` to be set, the Go proxy that got
that traffic re-routed it to `localhost:80`, which results in the CLI
failing.

I've opened an [upstream PR in the `global-agent`](gajus/global-agent#59)
repo to not proxy traffic that should reach sockets in the first place.
However, until this is fixed, we should simply use a custom agent for
docker modem.

Author: tommyknows

lib/docker.ts

@@ -81,6 +81,13 @@ class Docker {
     );
 
     const modem = new Modem();
+    // Depending on how `DOCKER_HOST` is set, we might connect to a socket or an
+    // HTTP server. However, the default http.globalAgent might be setup to use
+    // HTTP_PROXY, which we do not want to do when connecting to a socket. As
+    // such, if the socketPath is set, we do not use the global agent.
+    if (modem.socketPath !== "") {
+      modem.agent = false; // causes a new Agent with default values to be used.
+    }
 
     return new Promise<void>((resolve, reject) => {
       modem.dial(request, (err, stream: Stream) => {