feat: Add two abstraction helper methods

These methods are `IsIdenticalTo` and `IsEmpty`.

Author: nima

digest.go

@@ -30,7 +30,7 @@ import (
 //
 // The following is an example of the contents of Digest types:
 //
-// 	sha256:7173b809ca12ec5dee4506cd86be934c4596dd234ee82c0662eac04a8c2c71dc
+//	sha256:7173b809ca12ec5dee4506cd86be934c4596dd234ee82c0662eac04a8c2c71dc
 //
 // This allows to abstract the digest behind this type and work only in those
 // terms.
@@ -146,6 +146,16 @@ func (d Digest) String() string {
 	return string(d)
 }
 
+// IsIdenticalTo compares this digest to any other, inclusive of the hashing algorithm used
+func (d Digest) IsIdenticalTo(o Digest) bool {
+	return string(d) == string(o)
+}
+
+// IsEmpty does what it says (an empty digest is an empty string)
+func (d Digest) IsEmpty() bool {
+	return len(d) == 0
+}
+
 func (d Digest) sepIndex() int {
 	i := strings.Index(string(d), ":")