Add configurable User-Agent via USER_AGENT env var

desktop/context.go

@@ -3,7 +3,6 @@ package desktop
 import (
 	"context"
 	"fmt"
-	"github.com/docker/model-cli/pkg/types"
 	"net/http"
 	"net/url"
 	"os"
@@ -16,6 +15,7 @@ import (
 	"github.com/docker/cli/cli/context/docker"
 	clientpkg "github.com/docker/docker/client"
 	"github.com/docker/model-cli/pkg/standalone"
+	"github.com/docker/model-cli/pkg/types"
 	"github.com/docker/model-runner/pkg/inference"
 )
 
@@ -155,6 +155,10 @@ func DetectContext(ctx context.Context, cli *command.DockerCli) (*ModelRunnerCon
 		client = http.DefaultClient
 	}
 
+	if userAgent := os.Getenv("USER_AGENT"); userAgent != "" {
+		setUserAgent(client, userAgent)
+	}
+
 	// Success.
 	return &ModelRunnerContext{
 		kind:      kind,
@@ -183,3 +187,39 @@ func (c *ModelRunnerContext) URL(path string) string {
 func (c *ModelRunnerContext) Client() DockerHttpClient {
 	return c.client
 }
+
+func setUserAgent(client DockerHttpClient, userAgent string) {
+	if httpClient, ok := client.(*http.Client); ok {
+		transport := httpClient.Transport
+		if transport == nil {
+			transport = http.DefaultTransport
+		}
+
+		httpClient.Transport = &userAgentTransport{
+			userAgent: userAgent,
+			transport: transport,
+		}
+	}
+}
+
+type userAgentTransport struct {
+	userAgent string
+	transport http.RoundTripper
+}
+
+func (u *userAgentTransport) RoundTrip(req *http.Request) (*http.Response, error) {
+	reqClone := req.Clone(req.Context())
+
+	existingUA := reqClone.UserAgent()
+
+	var newUA string
+	if existingUA != "" {
+		newUA = existingUA + " " + u.userAgent
+	} else {
+		newUA = u.userAgent
+	}
+
+	reqClone.Header.Set("User-Agent", newUA)
+
+	return u.transport.RoundTrip(reqClone)
+}