diff -r d3c775ea2d0c -r 887cd09ea943 configure.ac
--- a/configure.ac	Mon Jun 26 21:38:06 2006 +0000
+++ b/configure.ac	Tue Jul 11 22:14:52 2006 +0000
@@ -15,7 +15,27 @@
 
 dnl Checks for libraries.
 PKG_CHECK_MODULES([GTK], [libgnomecanvasmm-2.6 >= 2.6.0 gtkmm-2.4 >= 2.6])
-PKG_CHECK_MODULES([LEMON], [lemon >= 0.5])
+PKG_CHECK_MODULES([LEMON_0_5], [lemon >= 0.5],
+  [lemon_0_5_found=yes], [
+    AC_MSG_RESULT([no])
+    lemon_0_5_found=no])
+PKG_CHECK_MODULES([LEMON_SVN_HEAD], [lemon = svn-head],
+  [lemon_svn_head_found=yes], [
+    AC_MSG_RESULT([no])
+    lemon_svn_head_found=no])
+if test x"$lemon_0_5_found" = x"no" -a x"$lemon_svn_head_found" = x"no"; then
+  AC_MSG_ERROR([LEMON not found.])
+else
+  if test x"$lemon_svn_head_found" = x"yes"; then
+    LEMON_CFLAGS="$LEMON_SVN_HEAD_CFLAGS"
+    LEMON_LIBS="$LEMON_SVN_HEAD_LIBS"
+  else
+    LEMON_CFLAGS="$LEMON_0_5_CFLAGS"
+    LEMON_LIBS="$LEMON_0_5_LIBS"
+  fi
+  AC_SUBST(LEMON_CFLAGS)
+  AC_SUBST(LEMON_LIBS)
+fi
 
 dnl Checks for header files.
 AC_CHECK_HEADERS([libintl.h locale.h])