Clarify the documentation of Parse to state its job is to parse, not validate, strings. (#135)

Author: bormanp

Diff for: uuid.go

@@ -56,11 +56,15 @@ func IsInvalidLengthError(err error) bool {
 	return ok
 }
 
-// Parse decodes s into a UUID or returns an error.  Both the standard UUID
-// forms of xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx and
-// urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx are decoded as well as the
-// Microsoft encoding {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx} and the raw hex
-// encoding: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx.
+// Parse decodes s into a UUID or returns an error if it cannot be parsed.  Both
+// the standard UUID forms defined in RFC 4122
+// (xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx and
+// urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx) are decoded.  In addition,
+// Parse accepts non-standard strings such as the raw hex encoding
+// xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx and 38 byte "Microsoft style" encodings,
+// e.g.  {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}.  Only the middle 36 bytes are
+// examined in the latter case.  Parse should not be used to validate strings as
+// it parses non-standard encodings as indicated above.
 func Parse(s string) (UUID, error) {
 	var uuid UUID
 	switch len(s) {