git push .git/description file
You could store a description (or .description, if you don't want it to be visible) in the root of your repo, and then symlink .git/description to that in each repo, like so:
repo/ .description .git/ description -> ../.descriptionYou'd have to set up the symlink manually in each of your repos, but you'd only have to do that once (when the repo is created).
Or you could use a post-receive hook to copy your tracked description file into .git/description. You'd have to set up that hook on each remote repo, too, but again, that would only need to happen once (when the repo is created).