Sometimes, after you mess up too much with your Git repository, it ends up with a couple useless objects, which are no longer referenced anywhere.
I created this alias a while ago, collected from sources I don’t remember anymore, to perform a cleanup in the repository. It’s particularly useful right after a git fetch:
alias gitcleanrepo='git fetch origin --prune && git -c gc.reflogExpire=0 -c gc.reflogExpireUnreachable=0 -c gc.rerereresolved=0 -c gc.rerereunresolved=0 -c gc.pruneExpire=now gc "$@"'