Adds rest config builder to include new user agent

Signed-off-by: joshvanl <vleeuwenjoshua@gmail.com>

pkg/util/BUILD.bazel

@@ -12,6 +12,7 @@ go_library(
     deps = [
         "//pkg/apis/certmanager/v1:go_default_library",
         "@io_k8s_apimachinery//pkg/apis/meta/v1/validation:go_default_library",
+        "@io_k8s_client_go//rest:go_default_library",
     ],
 )
 
@@ -23,7 +24,10 @@ go_test(
         "version_test.go",
     ],
     embed = [":go_default_library"],
-    deps = ["@com_github_stretchr_testify//assert:go_default_library"],
+    deps = [
+        "@com_github_stretchr_testify//assert:go_default_library",
+        "@io_k8s_client_go//rest:go_default_library",
+    ],
 )
 
 filegroup(

pkg/util/useragent.go

@@ -18,15 +18,24 @@ package util
 
 import (
 	"bytes"
+	"fmt"
 	"strings"
 	"unicode"
 	"unicode/utf8"
 
 	"k8s.io/apimachinery/pkg/apis/meta/v1/validation"
+	"k8s.io/client-go/rest"
 )
 
-// CertManagerUserAgent is the user agent that http clients in this codebase should use
-var CertManagerUserAgent = "cert-manager/" + version()
+// RestConfigWithUserAgent returns a copy of the Kubernetes REST config with
+// the User Agent set which includes the optional component strings given.
+func RestConfigWithUserAgent(restConfig *rest.Config, component ...string) *rest.Config {
+	restConfig = rest.CopyConfig(restConfig)
+	restConfig.UserAgent = fmt.Sprintf("%s/%s (%s) cert-manager/%s",
+		strings.Join(append([]string{"cert-manager"}, component...), "-"),
+		version(), VersionInfo().Platform, VersionInfo().GitCommit)
+	return restConfig
+}
 
 // PrefixFromUserAgent takes the characters preceding the first /, quote
 // unprintable character and then trim what's beyond the FieldManagerMaxLength

pkg/util/useragent_test.go

@@ -17,11 +17,48 @@ limitations under the License.
 package util
 
 import (
+	"runtime"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+	"k8s.io/client-go/rest"
 )
 
+func Test_RestConfigWithUserAgent(t *testing.T) {
+	AppGitCommit = "test-commit"
+
+	tests := map[string]struct {
+		component     []string
+		expRestConfig rest.Config
+	}{
+		"if no component name given, expect just cert-manager field manager": {
+			component: nil,
+			expRestConfig: rest.Config{
+				UserAgent: "cert-manager/canary-test-commit (" + runtime.GOOS + "/" + runtime.GOARCH + ") cert-manager/test-commit",
+			},
+		},
+		"if single component name given, expect cert-manager with single component field manager": {
+			component: []string{"controller"},
+			expRestConfig: rest.Config{
+				UserAgent: "cert-manager-controller/canary-test-commit (" + runtime.GOOS + "/" + runtime.GOARCH + ") cert-manager/test-commit",
+			},
+		},
+		"if multiple component names given, expect cert-manager with multiple component field manager": {
+			component: []string{"controller", "issuing-foo", "bar"},
+			expRestConfig: rest.Config{
+				UserAgent: "cert-manager-controller-issuing-foo-bar/canary-test-commit (" + runtime.GOOS + "/" + runtime.GOARCH + ") cert-manager/test-commit",
+			},
+		},
+	}
+
+	for name, test := range tests {
+		t.Run(name, func(t *testing.T) {
+			gotRestConfig := RestConfigWithUserAgent(new(rest.Config), test.component...)
+			assert.Equal(t, &test.expRestConfig, gotRestConfig)
+		})
+	}
+}
+
 // Adapted from
 // https://github.com/kubernetes/apiserver/blob/cecf3a2e57ffdfa8f3b36db4ee0c44e59ad656e9/pkg/endpoints/handlers/create_test.go#L24
 func Test_PrefixFromUserAgent(t *testing.T) {