Git? But you should be separating your lists.
Put the mirrors in separate files in the /etc/apt/sources.list.d/
directory.
This way if you need all you fabric mirrors, copy /etc/apt/sources.list.d/fabric.list
.
This will be changeable by something like puppet or saltstack. If you then /etc/apt/preference
correctly, when fabric mirrors are present then they will be used in preference to other mirrors (where there is a conflict of package versions and dependencies).