Pushing rails app to heroku not working

I'm trying to use git push heroku master to upload my rails 3 app to heroku, but I keep getting the following error:

-----> Heroku receiving push
-----&g开发者_如何转开发t; Removing .DS_Store files
-----> Rails app detected
!     Heroku Bamboo does not include any Rails gems by default.
!     You'll need to declare it in either .gems or Gemfile.
!     See http://docs.heroku.com/gems for details on specifying gems.
!     Heroku push rejected, no Rails gem specified.

error: hooks/pre-receive exited with error code 1

I've tried deleting the on the heroku website and starting again, i've also tried wiping out my git repo and doing init again, and I keep getting the same error. My Gemfile is as follows:

source :rubygems 

gem 'rails', '3.0.3'
gem 'recaptcha', :require => 'recaptcha/rails'
gem 'devise', '1.1.3'
gem 'acts-as-taggable-on'
gem 'ruby-debug'
# for sass
gem 'haml'
gem 'mocha'
gem 'ruby-pg'

I've run bundle package to package teh gems into vendor cache, but it doesn't seem to change the result.

I upgraded this app from rails 2.3, so i'm wondering if that has anything to do with it?

This is the answer I got from Heroku:

Hi,

The problem seems to be that your Gemfile is called GemFile. While that'll work on some platforms like the Mac, that won't work on a strictly case-sensitive filesystem, such as ours.

In order to rename the file in a case-retaining, case-insensitive file system like HFS or NTFS, you'll need to do it in two steps:

git mv GemFile Gemfile.temp
git mv Gemfile.temp Gemfile

Try adding these to your Gemfile

gem 'pg' # Heroku's DB runs on postgresql
gem 'heroku'