util.chunkbuffer: special case reading everything

The new code results in simpler logic within the while loop. It is also
faster since we avoid performing operations on the queue and buf
collections. However, there shouldn't be any super hot loops for this
since the whole point of chunkbuffer is to avoid reading large amounts
of data at once. This does, however, make it easier to optimize
chunkbuffer in a subsequent patch.

mercurial/util.py

@@ -1292,10 +1292,13 b' class chunkbuffer(object):'
         Returns less than L bytes if the iterator runs dry.
 
         If size parameter is omitted, read everything"""
+        if l is None:
+            return ''.join(self.iter)
+
         left = l
         buf = []
         queue = self._queue
-        while left is None or left > 0:
+        while left > 0:
             # refill the queue
             if not queue:
                 target = 2**18
@@ -1308,9 +1311,8 b' class chunkbuffer(object):'
                     break
 
             chunk = queue.popleft()
-            if left is not None:
-                left -= len(chunk)
-            if left is not None and left < 0:
+            left -= len(chunk)
+            if left < 0:
                 queue.appendleft(chunk[left:])
                 buf.append(chunk[:left])
             else: