Reopen STDIN when Overcommit isn't installed

Git hooks are not run in an interactive context, meaning STDIN isn't a
TTY and so we can't read user input.

The solution to this is to reopen STDIN to manually wire up a TTY.

Change-Id: Ia12c5cceba26d95313bdf1b1f9d271ef3a421248
Reviewed-on: http://gerrit.causes.com/35618
Reviewed-by: Shane da Silva <shane@causes.com>
Tested-by: Shane da Silva <shane@causes.com>

Author: sds

template-dir/hooks/overcommit-hook

@@ -22,6 +22,9 @@ rescue LoadError
   puts 'Overcommit is not installed. Install it to manage git hooks for ' <<
        'this repository? (y/n)'
 
+  # If the hook isn't interactive, we need to map STDIN to keyboard manually
+  STDIN.reopen('/dev/tty') if STDIN.eof?
+
   if (answer = gets) && answer.strip.downcase.start_with?('y')
     if system('gem install overcommit')
       require 'overcommit'