util: add 'mode' argument to popen()

mercurial/util.py

@@ -1044,12 +1044,12 b" if os.name == 'nt':"
         # through the current COMSPEC. cmd.exe suppress enclosing quotes.
         return '"' + cmd + '"'
 
-    def popen(command):
+    def popen(command, mode='r'):
         # Work around "popen spawned process may not write to stdout
         # under windows"
         # http://bugs.python.org/issue1366
         command += " 2> %s" % nulldev
-        return os.popen(quotecommand(command))
+        return os.popen(quotecommand(command), mode)
 
     def explain_exit(code):
         return _("exited with status %d") % code, code
@@ -1212,8 +1212,8 b' else:'
     def quotecommand(cmd):
         return cmd
 
-    def popen(command):
-        return os.popen(command)
+    def popen(command, mode='r'):
+        return os.popen(command, mode)
 
     def testpid(pid):
         '''return False if pid dead, True if running or not sure'''