make sure a GNU diffutils are available as a last resort for merging

monotone/monotone.spec

@@ -45,7 +45,7 @@ Patch0:       monotone.patch
 Prefix:       %{l_prefix}
 BuildRoot:    %{l_buildroot}
 BuildPreReq:  OpenPKG, openpkg >= 20040130, gcc, gcc::with_cxx = yes
-PreReq:       OpenPKG, openpkg >= 20040130, apg
+PreReq:       OpenPKG, openpkg >= 20040130, apg, diffutils
 BuildPreReq:  boost, zlib
 PreReq:       boost, zlib
 AutoReq:      no