Check for multiline shebang script hacks

Fixes #8

lib/linguist/blob_helper.rb

@@ -308,7 +308,7 @@ module Linguist
       # Fail fast if blob isn't viewable?
       return unless viewable?
 
-      if data && (match = data.match(/(.+)\n?/)) && (bang = match[0]) =~ /^#!/
+      if data && (match = lines[0].match(/(.+)\n?/)) && (bang = match[0]) =~ /^#!/
         bang.sub!(/^#! /, '#!')
         tokens = bang.split(' ')
         pieces = tokens.first.split('/')
@@ -325,6 +325,16 @@ module Linguist
           script.sub! $1, ''
         end
 
+        # Check for multiline shebang hacks that exec themselves
+        #
+        #   #!/bin/sh
+        #   exec foo "$0" "$@"
+        #
+        if script == 'sh' &&
+            lines[0...5].any? { |l| l.match(/exec (\w+).+\$0.+\$@/) }
+          script = $1
+        end
+
         script
       end
     end