Do you really want to go through this extra effort to achieve the function you want? If I understand correctly, it's like you want a button on github or googlecode with "deploy to appspot" and technically I think it is doable if you really want but I suggested this as a feature to googlecode several years ago: Editable repository, which google started with recently so that you can edit your files directly in the repository, and I also suggest deployment directly from googlecode like a button saying "deploy my project to appspot" and then we don't need local development anymore.
However the story is that they dropped that feature request and I can understand why since a lot of things can go wrong and your repository might not be a standard place to deploy from since it is not uncommon to include files to the project that are not in the repository and that seems impossible if you have some part of the code that you must change a little right before deployment without versioning that code ie a password or a secret key that you need to deploy without putting it in source control.
I called this idea "3in1": The repository can 3 things in one: 1) versioning 2) edit files and 3) deploy the files where only the first is a core function of the repository.
You could setup a schedular deployment machine that runs a cron job or so that takes the latest code from your repository and deploys it if it changed if you really want to enable this feature.