Latest builtin-commit series

Hi,

I sent out a new builtin-commit patch series last night, and figured I
should have written a cover letter to describe the changes there.
Better late than never:

      * rebase to Pierres strbuf changes.  Note, there is still some
        strbuf tweaking required, to let stripspace work on a strbuf.
        Also, I changed the semantics of stripspace to always add a
        newline if the last line doesn't have one.  I believe the
        current odd semantics (always remove the last newline) comes
        from not being able to easily add a newline, but now that it's a
        strbuf, that's easy.