http://www.kernel.org/pub/software/scm/git/docs/git-gc.html http://www.kernel.org/pub/software/scm/git/docs/git-gc.html "git gc tries very hard to be safe abou

http://www.kernel.org/pub/software/scm/git/docs/git-gc.html http://www.kernel.org/pub/software/scm/git/docs/git-gc.html "git gc tries very hard to be safe about the garbage it collects. In particular, it will keep not only objects referenced by your current set of branches and tags, but also objects referenced by the index, remote tracking branches, refs saved by git filter-branch in refs/original/, or reflogs (which may reference commits in branches that were later amended or rewound)."