+#
+# val: '0' | '1' ;
+#
+# fuzzyopt: '--display-fuzzy=' val ;
+#
+# untranslatedopt: '--display-untranslated=' val ;
+#
+# option: fuzzyopt
+# | untranslatedopt
+# ;
+# options: | options option
+# ;
+#
+# revspec: revision-tag # e.g. 46c00bab7
+# | 'HEAD' relative-rev # e.g. HEAD~3, HEAD-3
+# | '-' number # -1 == previous commit of the following po-file
+# ;
+#
+# revision: '-r' revspec ;
+#
+# filespecold: revision | filespec ;
+#
+# filespec: # path to existing po-file
+#
+# filespecnew: filespec ;
+#
+# files: filespecold filespecnew ;
+#
+# diff: 'diff_po.pl' ' ' options files
+#