I know how to set a new type. What I want to do is modify an existing type. I want to add haml files to the ruby type. I could probably use --set-type and redefine the ruby type but I don't know how to redefine it and still include files called 'Rakefile' and files where the first line indicates that it is an executable Ruby script (First line matches /^#!.*\bruby/)
Here is the existing documentation for the ruby type:
ruby .rb .rhtml .rjs .rxml .erb .rake .spec; Rakefile; First line matches /^#!.*\bruby/