Apply value of http_unix_socket if present in config

pkg/cmd/factory/http.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/cli/cli/api"
 	"github.com/cli/cli/internal/ghinstance"
+	"github.com/cli/cli/internal/httpunix"
 	"github.com/cli/cli/pkg/iostreams"
 )
 
@@ -59,6 +60,29 @@ type configGetter interface {
 // generic authenticated HTTP client for commands
 func NewHTTPClient(io *iostreams.IOStreams, cfg configGetter, appVersion string, setAccept bool) (*http.Client, error) {
 	var opts []api.ClientOption
+
+	// We need to check and potentially add the unix socket roundtripper option
+	// before adding any other options, since if we are going to use the unix
+	// socket transport, it needs to form the base of the transport chain
+	// represented by invocations of opts...
+	//
+	// Another approach might be to change the signature of api.NewHTTPClient to
+	// take an explicit base http.RoundTripper as its first parameter (it
+	// currently defaults internally to http.DefaultTransport), or add another
+	// variant like api.NewHTTPClientWithBaseRoundTripper. But, the only caller
+	// which would use that non-default behavior is right here, and it doesn't
+	// seem worth the cognitive overhead everywhere else just to serve this one
+	// use case.
+	unixSocket, err := cfg.Get("", "http_unix_socket")
+	if err != nil {
+		return nil, err
+	}
+	if unixSocket != "" {
+		opts = append(opts, api.ClientOption(func(http.RoundTripper) http.RoundTripper {
+			return httpunix.NewRoundTripper(unixSocket)
+		}))
+	}
+
 	if verbose := os.Getenv("DEBUG"); verbose != "" {
 		logTraffic := strings.Contains(verbose, "api")
 		opts = append(opts, api.VerboseLog(io.ErrOut, logTraffic, io.IsStderrTTY()))