add http head based digest comparison to avoid dockerhub rate limits

pkg/types/container.go

@@ -0,0 +1,26 @@
+package types
+
+import "github.com/docker/docker/api/types"
+
+// Container is a docker container running an image
+type Container interface {
+	ContainerInfo() *types.ContainerJSON
+	ID() string
+	IsRunning() bool
+	Name() string
+	ImageID() string
+	ImageName() string
+	Enabled() (bool, bool)
+	IsMonitorOnly() bool
+	Scope() (string, bool)
+	Links() []string
+	ToRestart() bool
+	IsWatchtower() bool
+	StopSignal() string
+	HasImageInfo() bool
+	ImageInfo() *types.ImageInspect
+	GetLifecyclePreCheckCommand() string
+	GetLifecyclePostCheckCommand() string
+	GetLifecyclePreUpdateCommand() string
+	GetLifecyclePostUpdateCommand() string
+}

pkg/types/registry_credentials.go

@@ -0,0 +1,7 @@
+package types
+
+// RegistryCredentials is a credential pair used for basic auth
+type RegistryCredentials struct {
+	Username string
+	Password string // usually a token rather than an actual password
+}

pkg/types/token_response.go

@@ -0,0 +1,6 @@
+package types
+
+// TokenResponse is returned by the registry on successful authentication
+type TokenResponse struct {
+	Token string `json:"token"`
+}