Being lazy i created a pushy.sh script in my ruby app to repeatedly call this command. However, it will only work from the root of the project, and not the sub folder your ruby app is in. So for ruby/app/pushy.sh to run it had to call the following.
(cd ../../ && git subtree push --prefix www/tutapp heroku master)
The git commands to run from a different directory didn't work for me. i.e. i couldn't get the following to work.
git --git-dir=../../.git --work-tree=../../ subtree <etc. etc>
Being lazy i created a pushy.sh script in my ruby app to repeatedly call this command. However, it will only work from the root of the project, and not the sub folder your ruby app is in. So for ruby/app/pushy.sh to run it had to call the following.
The git commands to run from a different directory didn't work for me. i.e. i couldn't get the following to work.