diff --git a/mercurial/pycompat.py b/mercurial/pycompat.py
--- a/mercurial/pycompat.py
+++ b/mercurial/pycompat.py
@@ -316,3 +316,7 @@
     rawinput = raw_input
 
 isjython = sysplatform.startswith('java')
+
+isdarwin = sysplatform == 'darwin'
+isposix = osname == 'posix'
+iswindows = osname == 'nt'