If anyone is interested, there's a tiny utility I've used daily for years to do this: https://github.com/bitjson/wip

Each time you run `wip`, all current work is committed. When you run the squashing utility `naenae` (autocomplete: `nae + Tab`), the most recent line of "WIP" commits is saved to a `wip-archives/[branch]/[timestamp]` branch for safe keeping, the commits are all squashed in place, and you're left in your default git editor to define the commit message. It also handles unusual situations, like using `wip` for the first commit (in which case, `git reset HEAD^` will return an error).

Being able to set a sort of "WIP checkpoint" in the current working directory makes it really easy to start or back out of big changes, and it can be very useful to check back in past WIP commits to grab segments of code you previously threw away.