Add Forth extensions .f and .for; add heuristics for Forth and FORTRAN.

lib/linguist/heuristics.rb

@@ -36,6 +36,9 @@ module Linguist
         if languages.all? { |l| ["AsciiDoc", "AGS Script"].include?(l) }
           result = disambiguate_asc(data)
         end
+        if languages.all? { |l| ["FORTRAN", "Forth"].include?(l) }
+          result = disambiguate_f(data)
+        end
         return result
       end
     end
@@ -138,6 +141,16 @@ module Linguist
       matches
     end
 
+    def self.disambiguate_f(data)
+      matches = []
+      if /^: /.match(data)
+        matches << Language["Forth"]
+      elsif /^([c*][^a-z]|      subroutine\s)/i.match(data)
+        matches << Language["FORTRAN"]
+      end
+      matches
+    end
+
     def self.active?
       !!ACTIVE
     end