don't save comments in commit message

The comment lines are auto generated by git, so there is no point in saving them; it's often confusing to see the old list of changes-to-be-committed that doesn't correspond to the current commit.

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###### Possible concern:
This could lose some info if the user puts a trailing comment themselves. I don't think that's worth coding for as there is no benefit (that I can think of) to writing manual comments in a commit message.