Rename Format method to Encode.

cid.go

@@ -338,8 +338,9 @@ func (c *Cid) StringOfBase(base mbase.Encoding) (string, error) {
 	}
 }
 
-// Format return the string representation of a Cid
-func (c *Cid) Format(base mbase.Encoder) string {
+// Encode return the string representation of a Cid in a given base
+// when applicable
+func (c *Cid) Encode(base mbase.Encoder) string {
 	switch c.version {
 	case 0:
 		return c.hash.B58String()

cid_test.go

@@ -153,11 +153,11 @@ func TestBasesMarshaling(t *testing.T) {
 
 		assertEqual(t, cid, out2)
 
-		prefix, err := mbase.NewEncoder(b)
+		encoder, err := mbase.NewEncoder(b)
 		if err != nil {
 			t.Fatal(err)
 		}
-		s2 := cid.Format(prefix)
+		s2 := cid.Encode(encoder)
 		if s != s2 {
 			t.Fatalf("'%s' != '%s'", s, s2)
 		}