+def inverse_relpath (path, relpath):
+ """Given two paths, the second relative to the first,
+ return the first path relative to the second."""
+ if os.path.isabs (relpath):
+ return os.path.abspath (path)
+ relparts = []
+ parts = os.path.normpath (path).split (os.path.sep)
+ for part in os.path.normpath (relpath).split (os.path.sep):
+ if part == '..':
+ relparts.append (parts[-1])
+ parts.pop ()
+ else:
+ relparts.append ('..')
+ parts.append (part)
+ return os.path.sep.join (relparts[::-1])
+