+* Updating
+
+The use of submodules make things somewhat different because git does
+not support recursive operations: submodules must be taken care of
+explicitly by the user.
+
+** Updating Bison
+
+If you pull a newer version of a branch, say via `git pull', you might
+import requests for updated submodules. A simple `git diff' will
+reveal if the current version of the submodule (i.e., the actual
+contents of the gnulib directory) and the current request from the
+subscriber (i.e., the reference of the version of gnulib that the
+Bison reporitory requests) differ. To upgrade the submodules (i.e.,
+to check out the version that is actually requested by the subscriber,
+run `git submodule update'.
+
+ $ git pull
+ $ git submodule update
+
+** Updating a submodule
+To update a submodule, say gnulib, do as follows:
+
+Get the most recent version of the master branch from git.
+
+ $ cd gnulib
+ $ git fetch
+ $ git checkout -b master --track origin/master
+
+Make sure Bison can live with that version of gnulib.
+
+ $ cd ..
+ $ ./bootstrap
+ $ make distcheck
+
+Register your changes.
+
+ $ git checkin ...
+