digest: remove stuttering ParseDigest function

Signed-off-by: Stephen J Day <stephen.day@docker.com>

digest/digest.go

@@ -63,12 +63,16 @@ var (
 
 // ParseDigest parses s and returns the validated digest object. An error will
 // be returned if the format is invalid.
-func ParseDigest(s string) (Digest, error) {
+func Parse(s string) (Digest, error) {
 	d := Digest(s)
-
 	return d, d.Validate()
 }
 
+// ParseDigest is deprecated. Use Parse.
+func ParseDigest(s string) (Digest, error) {
+	return Parse(s)
+}
+
 // FromReader returns the most valid digest for the underlying content using
 // the canonical digest algorithm.
 func FromReader(rd io.Reader) (Digest, error) {