1 files changed, 94 insertions, 0 deletions
diff --git a/pkg/v1/remote/transport/useragent.go b/pkg/v1/remote/transport/useragent.go
new file mode 100644
index 0000000..74a9e71
--- /dev/null
+++ b/pkg/v1/remote/transport/useragent.go
@@ -0,0 +1,94 @@
+// Copyright 2019 Google LLC All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package transport
+
+import (
+	"fmt"
+	"net/http"
+	"runtime/debug"
+)
+
+var (
+	// Version can be set via:
+	// -ldflags="-X 'github.com/google/go-containerregistry/pkg/v1/remote/transport.Version=$TAG'"
+	Version string
+
+	ggcrVersion = defaultUserAgent
+)
+
+const (
+	defaultUserAgent = "go-containerregistry"
+	moduleName       = "github.com/google/go-containerregistry"
+)
+
+type userAgentTransport struct {
+	inner http.RoundTripper
+	ua    string
+}
+
+func init() {
+	if v := version(); v != "" {
+		ggcrVersion = fmt.Sprintf("%s/%s", defaultUserAgent, v)
+	}
+}
+
+func version() string {
+	if Version != "" {
+		// Version was set via ldflags, just return it.
+		return Version
+	}
+
+	info, ok := debug.ReadBuildInfo()
+	if !ok {
+		return ""
+	}
+
+	// Happens for crane and gcrane.
+	if info.Main.Path == moduleName {
+		return info.Main.Version
+	}
+
+	// Anything else.
+	for _, dep := range info.Deps {
+		if dep.Path == moduleName {
+			return dep.Version
+		}
+	}
+
+	return ""
+}
+
+// NewUserAgent returns an http.Roundtripper that sets the user agent to
+// The provided string plus additional go-containerregistry information,
+// e.g. if provided "crane/v0.1.4" and this modules was built at v0.1.4:
+//
+// User-Agent: crane/v0.1.4 go-containerregistry/v0.1.4
+func NewUserAgent(inner http.RoundTripper, ua string) http.RoundTripper {
+	if ua == "" {
+		ua = ggcrVersion
+	} else {
+		ua = fmt.Sprintf("%s %s", ua, ggcrVersion)
+	}
+	return &userAgentTransport{
+		inner: inner,
+		ua:    ua,
+	}
+}
+
+// RoundTrip implements http.RoundTripper
+func (ut *userAgentTransport) RoundTrip(in *http.Request) (*http.Response, error) {
+	in.Header.Set("User-Agent", ut.ua)
+	return ut.inner.RoundTrip(in)
+}