Drop sys.build_number. Add sys.subversion.
diff --git a/Doc/lib/libsys.tex b/Doc/lib/libsys.tex
index f8f015d..6a82d1b 100644
--- a/Doc/lib/libsys.tex
+++ b/Doc/lib/libsys.tex
@@ -27,10 +27,19 @@
\versionadded{2.0}
\end{datadesc}
-\begin{datadesc}{build_number}
- A string representing the Subversion revision that this Python executable
- was built from. This number is a string because it may contain a trailing
- 'M' if Python was built from a mixed revision source tree.
+\begin{datadesc}{subversion}
+ A triple (repo, branch, version) representing the Subversion
+ information of the Python interpreter.
+ \var{repo} is the name of the repository, \code{'CPython'}.
+ \var{branch} is the a string of one of the forms \code{'trunk'},
+ \code{'branches/name'} or \code{'tags/name'}.
+ \var{version} is the output of \code{svnversion}, if the
+ interpreter was built from a Subversion checkout; it contains
+ the revision number (range) and possibly a trailing 'M' if
+ there were local modifications. If the tree was exported
+ (or svnversion was not available), it is the revision of
+ \code{Include/patchlevel.h} if the branch is a tag. Otherwise,
+ it is \code{None}.
\versionadded{2.5}
\end{datadesc}