Increase the tag length limit from 30 to 128

Signed-off-by: Burke Libbey <burke.libbey@shopify.com>

graph/tags.go

@@ -19,7 +19,7 @@ import (
 const DEFAULTTAG = "latest"
 
 var (
-	validTagName = regexp.MustCompile(`^[\w][\w.-]{0,29}$`)
+	validTagName = regexp.MustCompile(`^[\w][\w.-]{0,127}$`)
 )
 
 type TagStore struct {