Add --plugins flag to velero install (#1930)

* Add plugins flag to install

Signed-off-by: Nolan Brubaker <brubakern@vmware.com>

pkg/builder/container_builder.go

@@ -17,6 +17,8 @@ limitations under the License.
 package builder
 
 import (
+	"strings"
+
 	corev1api "k8s.io/api/core/v1"
 )
 
@@ -35,6 +37,32 @@ func ForContainer(name, image string) *ContainerBuilder {
 	}
 }
 
+// ForPluginContainer is a helper builder specifically for plugin init containers
+func ForPluginContainer(image string, pullPolicy corev1api.PullPolicy) *ContainerBuilder {
+	volumeMount := ForVolumeMount("plugins", "/target").Result()
+	return ForContainer(getName(image), image).PullPolicy(pullPolicy).VolumeMounts(volumeMount)
+}
+
+// getName returns the 'name' component of a docker
+// image (i.e. everything after the last '/' and before
+// any subsequent ':')
+func getName(image string) string {
+	slashIndex := strings.LastIndex(image, "/")
+	colonIndex := strings.LastIndex(image, ":")
+
+	start := 0
+	if slashIndex > 0 {
+		start = slashIndex + 1
+	}
+
+	end := len(image)
+	if colonIndex > slashIndex {
+		end = colonIndex
+	}
+
+	return image[start:end]
+}
+
 // Result returns the built Container.
 func (b *ContainerBuilder) Result() *corev1api.Container {
 	return b.object
@@ -66,3 +94,8 @@ func (b *ContainerBuilder) Env(vars ...*corev1api.EnvVar) *ContainerBuilder {
 	}
 	return b
 }
+
+func (b *ContainerBuilder) PullPolicy(pullPolicy corev1api.PullPolicy) *ContainerBuilder {
+	b.object.ImagePullPolicy = pullPolicy
+	return b
+}