--- a/mercurial/util.py	Wed Feb 19 21:32:14 2014 -0800
+++ b/mercurial/util.py	Thu Feb 20 02:38:36 2014 +0100
@@ -1989,12 +1989,14 @@
         for source, hook in self._hooks:
             hook(*args)
 
-def debugstacktrace(msg='stacktrace', skip=0, f=sys.stderr):
+def debugstacktrace(msg='stacktrace', skip=0, f=sys.stderr, otherf=sys.stdout):
     '''Writes a message to f (stderr) with a nicely formatted stacktrace.
-    Skips the 'skip' last entries.
+    Skips the 'skip' last entries. By default it will flush stdout first.
     It can be used everywhere and do intentionally not require an ui object.
     Not be used in production code but very convenient while developing.
     '''
+    if otherf:
+        otherf.flush()
     f.write('%s at:\n' % msg)
     entries = [('%s:%s' % (fn, ln), func)
         for fn, ln, func, _text in traceback.extract_stack()[:-skip - 1]]
@@ -2002,6 +2004,7 @@
         fnmax = max(len(entry[0]) for entry in entries)
         for fnln, func in entries:
             f.write(' %-*s in %s\n' % (fnmax, fnln, func))
+    f.flush()
 
 # convenient shortcut
 dst = debugstacktrace