[BUG] Git add <device file> silently fails

Hello,

there is code in read-cache.c:add_to_index() which checks if a file to be added is a regular file, directory, or symlink; this function otherwise error()s out. It looks as if add_to_index() is supposed to be called via:

  builtin/add.c:update_callback() ->
    read-cache.c:add_file_to_index() ->
      read-cache.c:add_to_index()

However, when trying to add a device special file, update_callback() ends up never getting called, no error message is produced, and git add silently fails:

	$ sudo mknod foobar c 1 3
	$ git add foobar
   $ echo $?
	0

Maybe someone familiar with run_diff_files() can have a look?

Thanks, Andreas