Find back lost commits, especially useful when you are doing dirty things and want to `cherry-pick` an orphan commit (for instance):
```sh
git log --graph --reflog
```
Some explanations: `--graph` show the commit tree, which is useful to notice the orphan leafs, and `--reflog` shows the world all the dirtiness you've done.
If you noticed that your folder grows, you can manually cast the garbage collector on it. It should do it automatically, but not often enough according to my standards.