Fix posixpath.realpath() for multiple pardirs (fixes issue #6975).
diff --git a/Lib/posixpath.py b/Lib/posixpath.py
index 5b2513a..d65dc75 100644
--- a/Lib/posixpath.py
+++ b/Lib/posixpath.py
@@ -382,9 +382,11 @@
         if name == pardir:
             # parent dir
             if path:
-                path = dirname(path)
+                path, name = split(path)
+                if name == pardir:
+                    path = join(path, pardir, pardir)
             else:
-                path = name
+                path = pardir
             continue
         newpath = join(path, name)
         if not islink(newpath):