Earlier, I wrote:
> Complementing a bit without affecting W requires
>lengthy goto instructions.

Not true!  As a final thought on this neverending subject, consider:
        bcf     tmp,0           ;Use value of 0
        skpc                    ;if carry is 1
        bsf     tmp,0           ;if carry 0, use 1.
        rrf     tmp,f           ;New bit to carry bit.
This does require a temporary register, but not W.  It doesn't affect any
status bits except carry.  It can be made conditional by skipping the rrf
conditionally.