--- a/mercurial/util.py	Sun Jul 25 10:05:38 2010 +0900
+++ b/mercurial/util.py	Sun Jul 25 13:10:57 2010 +0200
@@ -914,7 +914,17 @@
     def __init__(self, in_iter):
         """in_iter is the iterator that's iterating over the input chunks.
         targetsize is how big a buffer to try to maintain."""
-        self.iter = iter(in_iter)
+        def splitbig(chunks):
+            for chunk in chunks:
+                if len(chunk) > 2**20:
+                    pos = 0
+                    while pos < len(chunk):
+                        end = pos + 2 ** 18
+                        yield chunk[pos:end]
+                        pos = end
+                else:
+                    yield chunk
+        self.iter = splitbig(in_iter)
         self.buf = ''
 
     def read(self, l):