Document where the nextval_project_id function is for MySQL

Signed-off-by: Shawn O. Pearce <sop@google.com>

Documentation/project-setup.txt

diff --git a/Documentation/project-setup.txt b/Documentation/project-setup.txt
index 0c95781..baa2f48 100644
--- a/Documentation/project-setup.txt
+++ b/Documentation/project-setup.txt
@@ -65,8 +65,8 @@
 
 [NOTE]
 On MySQL use `nextval_project_id()` and `nextval_branch_id()` to
-obtain the next value in the sequences.
-
+obtain the next value in the sequences.  These are contained in the
+`sql/mysql_nextval.sql` script, available from `java -jar gerrit.war --cat sql/mysql_nextval.sql`.
 
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