cliconfig: use a const for ".docker" string

Signed-off-by: Antonio Murdaca <runcom@redhat.com>

cliconfig/config.go

@@ -17,6 +17,7 @@ import (
 const (
 	// ConfigFileName is the name of config file
 	ConfigFileName = "config.json"
+	configFileDir  = ".docker"
 	oldConfigfile  = ".dockercfg"
 
 	// This constant is only used for really old config files when the
@@ -31,7 +32,7 @@ var (
 
 func init() {
 	if configDir == "" {
-		configDir = filepath.Join(homedir.Get(), ".docker")
+		configDir = filepath.Join(homedir.Get(), configFileDir)
 	}
 }
 

image/v1/imagev1.go

@@ -142,7 +142,7 @@ func rawJSON(value interface{}) *json.RawMessage {
 // ValidateID checks whether an ID string is a valid image ID.
 func ValidateID(id string) error {
 	if ok := validHex.MatchString(id); !ok {
-		return fmt.Errorf("image ID '%s' is invalid ", id)
+		return fmt.Errorf("image ID %q is invalid", id)
 	}
 	return nil
 }