--autodrop and drop!

Hi,

I really like git's autosquash, it's super useful, especially with git absorb. I use them while the MR/PR is in draft state and then do a clean-up when it's ready to be reviewed. I sometimes also make commits which shouldn't make into the final MR, so I was wondering about adding the `drop!` equivalent (maybe with `--autodrop`, or just also under `--autosquash`, but I'm leaning towards the former as sometimes I might want to clean things up while still keeping the temporary commits).

An example of where this is useful is when I'm making changes to the CI, so I will be running more CI pipelines than usual and end up caring about the speed of it. So I make a `drop! Ignore other CI jobs` commit.

If it's something reasonably easy for me to do, and someone thinks it's easier to put a couple of bullet-points on how to do it than do it, then I would be happy to try and implement it myself*

*I cannot promise timeliness, effort as/when I have the energy, but since I'm the one who cares about this feature I don't think that will be a problem.

Thanks, Robert