+our $masterinfoversion= 2; # version we understand.
+#
+# To extend the source-info.txt format:
+#
+# * Commods.pm:parse_info1
+# add code to parse new version
+#
+# * source-info.txt
+# add new information
+#
+# If new data should NOT be in master-info.txt too:
+#
+# * update-master-info:process_some_info
+# check that code for converting source-info to master-info
+# removes the extra info; add code to remove it if necessary
+#
+# * db-idempotent-populate
+# if database schema is extended, add code to copy data
+#
+# If new data DOES need to be in master-info.txt too:
+#
+# * Commods.pm:$masterinfoversion
+# increment
+#
+# * update-master-info:process_some_info
+# add code to convert new version to old, by removing
+# extra info conditionally depending on version