Short on disk space and have #git & #svn repos?
$ git fetch --all --prune
# drop all removed upstream branches. (you may want check them, if you want to keep them they are still listed as dangling commits by git fsck before you gc)
$ du -sh .git && git gc --aggressive && du -sh .git
13M .git
Enumerating[…]
6.5M .git
# for svn:
$ du -s -h .svn && svn cleanup && du -s -h .svn
1.5G .svn/
785M .svn/
# on a virtualbox svn checkout it saved 700MB.