need a final prompt

[jlevon]

Currently, a user sees:

Is this commit message ok? (y/n, Ctrl-C to abort) :

and if they say yes, then we immediately squash and merge the PR. There should be a final check that they really want to merge (rather than, say, just see the commit message for some other reason).

[timfoster]

This combined with issue #5 turned out to be due to us not dealing with $EDITOR values containing spaces. I'll close this and deal with it as part of issue #5, where we'll clarify the "is this commit message ok?" question while we're at it.