In error I edited the 'post-revprop-change' file instead of the 'pre-revprop-change' in the hooks directory.
The edit I made was to copy in the instructions described here which allow changes to be made to the log entry. Obviously this doesn't make sense for the 'post-revprop-change' hook so I would like to undo the change. A simple thing would be just to delete the executable, but as I overwrote the template, I would like to know what the know what instructions should exist in this file. Apologies if my question seems convoluted.