Support of the .pro file extension for Prolog.

lib/linguist/heuristics.rb

@@ -22,6 +22,9 @@ module Linguist
         if languages.all? { |l| ["ECL", "Prolog"].include?(l) }
           disambiguate_ecl(data, languages)
         end
+        if languages.all? { |l| ["IDL", "Prolog"].include?(l) }
+          disambiguate_pro(data, languages)
+        end
         if languages.all? { |l| ["TypeScript", "XML"].include?(l) }
           disambiguate_ts(data, languages)
         end
@@ -56,6 +59,16 @@ module Linguist
       matches
     end
 
+    def self.disambiguate_pro(data, languages)
+      matches = []
+      if (data.include?(":-"))
+        matches << Language["Prolog"]
+      else
+        matches << Language["IDL"]
+      end
+      matches
+    end
+
     def self.disambiguate_ts(data, languages)
       matches = []
       if (data.include?("</translation>"))

lib/linguist/languages.yml

@@ -1325,6 +1325,7 @@ Prolog:
   extensions:
   - .ecl
   - .pl
+  - .pro
 
 Protocol Buffer:
   type: markup