Using alternate working directory

Hi everybody!

I need some help with Git.

I'm making a script `gm` which lets me merge one branch into another without having either checked out. It works for some cases but not all. I'm trying to make it work for more cases.

I concluded that the best way to do it would be by using an alternate, temporary working directory instead of the repo itself.

This is my script:

     https://gist.github.com/cool-RR/6575042

Now, the problem is that when I try it, it gives these errors:

     git checkout-index: my_file is not in the cache and then error:
     my_file: cannot add to the index - missing --add option?

Anyone has any idea what to do?

P.S. I've also asked this on Stack Overflow, so whoever comes up with an answer can claim his 150 imaginary internet points on that question.

Thanks, Ram.