JS is minified if its average line length is greater than 100c

Fixes #27

lib/linguist/blob_helper.rb

@@ -151,6 +151,17 @@ module Linguist
       lines.grep(/\S/).size
     end
 
+    # Internal: Compute average line length.
+    #
+    # Returns Integer.
+    def average_line_length
+      if lines.any?
+        lines.inject(0) { |n, l| n += l.length } / lines.length
+      else
+        0
+      end
+    end
+
     # Public: Is the blob a generated file?
     #
     # Generated source code is supressed in diffs and is ignored by
@@ -166,16 +177,24 @@ module Linguist
     def generated?
       if ['.xib', '.nib', '.pbxproj'].include?(extname)
         true
-      elsif generated_coffeescript?
+      elsif generated_coffeescript? || minified_javascript?
         true
-      elsif extname == '.js'
-        # JS is minified if any lines are longer than 500c
-        lines.any? { |l| l.length > 500 }
       else
         false
       end
     end
 
+    # Internal: Is the blob minified JS?
+    #
+    # Consider JS minified if the average line length is
+    # greater then 100c.
+    #
+    # Returns true or false.
+    def minified_javascript?
+      return unless extname == '.js'
+      average_line_length > 100
+    end
+
     # Internal: Is the blob JS generated by CoffeeScript?
     #
     # Requires Blob#data