[devit]

Well then such a cache needs obviously to have limit to the disk space it uses and some sort of cache replacement policy, since if one can generate a zip file for each tag, that means that the total disk space of the cache is O(n^2) where n is the disk usage of the git repositories (imagine a single repository where each commit is tagged and adds a new file of constant size), so unless one's total disk space is a million/billion times larger than the disk space used by the repositories, it's guaranteed to fill the disk without such a limit.