datastore: Update AllocateIDs to take keys.

service/datastore/key.go

Index: service/datastore/key.go
diff --git a/service/datastore/key.go b/service/datastore/key.go
index 2071bfb7b2ad01ceed9c42592d5d6ba01fb6b053..85dd1c4508b95d05ae9d44f4a8a70feb6a927eb6 100644
--- a/service/datastore/key.go
+++ b/service/datastore/key.go
@@ -414,14 +414,27 @@ func (k *Key) GQL() string {
 }
 
 // Equal returns true iff the two keys represent identical key values.
-func (k *Key) Equal(other *Key) (ret bool) {
+func (k *Key) Equal(other *Key) bool {
+	return k.SameKind(other) && (k.LastTok() == other.LastTok())
+}
+
+// SameKind asserts that other refers to the same entity as k. This checks the
+// full lineage of the key.
+func (k *Key) SameKind(other *Key) (ret bool) {
 	ret = (k.appID == other.appID &&
 		k.namespace == other.namespace &&
 		len(k.toks) == len(other.toks))
 	if ret {
 		for i, t := range k.toks {
-			if ret = t == other.toks[i]; !ret {
-				return
+			if i == len(k.toks)-1 {
+				// Last token: check only Kind.
+				if ret = (t.Kind == other.toks[i].Kind); !ret {
+					return
+				}
+			} else {
+				if ret = t == other.toks[i]; !ret {
+					return
+				}
 			}
 		}
 	}