Fix small lint and unit test issues

Pull request ci was not running and caused these
minor issues to not be caught.

Signed-off-by: Derek McGowan <derek@mcgstyle.net> (github: dmcgowan)

digest/algorithm.go

@@ -79,7 +79,7 @@ func (a *Algorithm) Set(value string) error {
 	return nil
 }
 
-// New returns a new digester for the specified algorithm. If the algorithm
+// Digester returns a new digester for the specified algorithm. If the algorithm
 // does not have a digester implementation, nil will be returned. This can be
 // checked by calling Available before calling New.
 func (a Algorithm) Digester() Digester {

digest/digest.go

@@ -61,7 +61,7 @@ var (
 	ErrDigestUnsupported = fmt.Errorf("unsupported digest algorithm")
 )
 
-// ParseDigest parses s and returns the validated digest object. An error will
+// Parse parses s and returns the validated digest object. An error will
 // be returned if the format is invalid.
 func Parse(s string) (Digest, error) {
 	d := Digest(s)

reference/reference_test.go

@@ -1,6 +1,8 @@
 package reference
 
 import (
+	_ "crypto/sha256"
+	_ "crypto/sha512"
 	"encoding/json"
 	"strconv"
 	"strings"