diff -r 175e4b9d8a96 -r 76f295eaed86 mercurial/util.py
--- a/mercurial/util.py	Thu Jun 02 18:52:31 2011 +0800
+++ b/mercurial/util.py	Thu Jun 02 00:43:34 2011 +0300
@@ -1591,3 +1591,9 @@
     u = url(u)
     u.user = u.passwd = None
     return str(u)
+
+def isatty(fd):
+    try:
+        return fd.isatty()
+    except AttributeError:
+        return False