That's a scenario for branch-then-cherrypick :)

Branch, write test to expose bug, add debug aids, fix bug, switch branch, cherry pick the test & fix, delete debug branch.

Or just `git rebase -i origin/master` and delete the unnecessary commits without additional branching.

I have these in my WIP branches. When I’m ready to merge, I squash out some of the smaller commits, and then merge without fast-forward. Reduces noise and keeps a clear history of groups of work, at the expense of very cheap branching and local rebasing operations.