Set Up GIT Branching Repository Workflow

I need a web developer experienced in setting up GIT repository workflows for web development.
The successful candidate will have experience in PHP, SSH, Git, GitHub, BitBucket.

This GIT workflow must be suitable for Magento and Wordpress projects.

The set up we're looking for is as follows:

- development files located in local machine which have MAMP and GIT installed
- files are pushed to a staging site, ready to be previewed
- files are then merged from the staging site into the production/live site
- changes are automatically pushed and pulled between all locations
- enable 3rd party developers to clone the repository from a remote repository for making changes as needed
- 3rd party developers can update the staging site but not the production site
- any other recommendations??

We also require an explanation of how the workflow works, in case we need to make future tweaks.

Thanks