@@ -156,15 +156,20 @@

   "Return the commits reachable from the ref."

   (when limit-p

     (rotatef ref-id limit))

-  (labels ((iterate (queue accum &optional (count 0))

-             (if (or (when limit-p

-                       (= limit count))

-                     (null queue))

-                 accum

-                 (destructuring-bind (next . rest) queue

-                   (iterate (append rest

-                                    (co.fwoar.git::parents next))

-                     (cons next accum)

-                     (1+ count))))))

-    (iterate (list (ensure-ref ref-id))

-      ())))

+  (let ((seen (make-hash-table)))

+    (labels ((iterate (queue accum &optional (count 0))

+               (if (or (when limit-p

+                         (= limit count))

+                       (null queue))

+                   accum

+                   (destructuring-bind (next . rest) queue

+                     (let ((parents (co.fwoar.git::parents next)))

+                       (iterate (append rest parents)

+                         (if (gethash next seen)

+                             accum

+                             (progn

+                               (setf (gethash next seen) t)

+                               (cons next accum)))

+                         (1+ count)))))))

+      (iterate (list (ensure-ref ref-id))

+        ()))))