--- a/mercurial/httprepo.py	Sat Apr 30 19:36:48 2011 +0200
+++ b/mercurial/httprepo.py	Sun May 01 01:04:37 2011 +0800
@@ -76,7 +76,26 @@
         data = args.pop('data', None)
         headers = args.pop('headers', {})
         self.ui.debug("sending %s command\n" % cmd)
-        q = [('cmd', cmd)] + sorted(args.items())
+        q = [('cmd', cmd)]
+        headersize = 0
+        if len(args) > 0:
+            httpheader = self.capable('httpheader')
+            if httpheader:
+                headersize = int(httpheader.split(',')[0])
+        if headersize > 0:
+            # The headers can typically carry more data than the URL.
+            encargs = urllib.urlencode(sorted(args.items()))
+            headerfmt = 'X-Arg-%s'
+            contentlen = headersize - len(headerfmt % '000' + ': \r\n')
+            headernum = 0
+            for i in xrange(0, len(encargs), contentlen):
+                headernum += 1
+                header = headerfmt % str(headernum)
+                headers[header] = encargs[i:i + contentlen]
+            varyheaders = [headerfmt % str(h) for h in range(1, headernum + 1)]
+            headers['Vary'] = ','.join(varyheaders)
+        else:
+            q += sorted(args.items())
         qs = '?%s' % urllib.urlencode(q)
         cu = "%s%s" % (self._url, qs)
         req = urllib2.Request(cu, data, headers)