You don't need to keep their hashes because git keeps them for you. If you realise too late that things went terribly wrong, you can get the pre-rebase hashes with "git reflog". (It can take a little getting used to knowing how to identify them quickly after a rebase but they're there.)

Better yet, git reset ORIG_HEAD or whatever is usually sufficient[0]. The reflog is the general solution, but git's magic references do provide quite a few niceties.

https://www.man7.org/linux/man-pages/man7/gitrevisions.7.htm...