Put a link back to the index in every page footer

Signed-off-by: Shawn O. Pearce <sop@google.com>
diff --git a/Documentation/user-upload.txt b/Documentation/user-upload.txt
index 240013e..5bd64c7 100644
--- a/Documentation/user-upload.txt
+++ b/Documentation/user-upload.txt
@@ -317,3 +317,7 @@
 connection before data is sent.  This ensures that project owners
 can be certain any object available in their repository has been
 supplied under at least one valid agreement.
+
+GERRIT
+------
+Part of link:index.html[Gerrit Code Review]