[lmi] /etc/etckeeper/.git became enormous

[Greg Chicares]

It seems that etckeeper might never trigger garbage collection.
On a corporate server:

du -sh /etc/.git/objects/
11G     /etc/.git/objects/

git gc

du -sh /etc/.git/objects/
44M     /etc/.git/objects/

A tiny 11G file shouldn't matter in 2022, but this server mounts
various parts of the filesystem on distinct partitions.

I created a script to automate this, following the advice here:

https://www.turnkeylinux.org/forum/support/20111111/etckeeper-has-huge-git-repo-how-remove

#cat /etc/etckeeper/post-install.d/99git-gc
#!/bin/sh
exec git gc