"Phillip Wood via GitGitGadget" [off-list ref] writes:

From: Phillip Wood <redacted>

As $EDITOR is exported, setting it in one test affects all subsequent
tests. Avoid this by always setting it in a subshell. Also remove a
couple of unnecessary call to set_fake_editor where the editor does
not change the todo list.

True.

The fact that we need to do this makes me wonder if we want a
restore_editor (or a hardcoded "export EDITOR=:") that allows us not
to go to a subshell, as going to a subshell has its downsides (e.g.
we cannot use helpers that rely on being able to modify globals,
like test_commit and test_when_finished), but for now this looks OK.

Thanks.