convert ast versioning to mercurial
diff --git a/Doc/library/ast.rst b/Doc/library/ast.rst
index e2c0b6d..85081be 100644
--- a/Doc/library/ast.rst
+++ b/Doc/library/ast.rst
@@ -96,8 +96,8 @@
Abstract Grammar
----------------
-The module defines a string constant ``__version__`` which is the decimal
-Subversion revision number of the file shown below.
+The module defines a string constant ``__version__`` which is the Mercurial
+revision of the file shown below.
The abstract grammar is currently defined as follows: