Re: On-branch topic description support?

> For example, I do not think it is unreasonable to teach "git rebase
> [-i]" to special case a certain merge commit in the rebased range
> without any extra option, as long as the criteria to pick such a
> special "merge" is specific and narrow enough (a two-parent merge M
> whose tree matches that of one parent's tree (say M^1^{tree}), the
> other parent (say M^2) is an immediate ancestor of the bottommost
> commit of the range being rebased, or something like that).  And the
> way you "special case" it does not have to be tied to the way the
> "-r" option handles it, either.  
> 
> A possible design could go like this:
> 
>  * we recognize such a special merge commit;
> 
>  * we rebase the rest of the range, pretending as if that merge
>    commit did not exist and instead its children are all direct
>    child of one of its parent (say M^1), using the options given (so
>    "-r" would affect how other merges in the rebased range is
>    handled).
> 
>  * after everything is done, we create a new empty merge commit at
>    the top, merging the bottom of the range and the tip of the range
>    as its parents, using the log message from original M.  This can
>    be done totally outside of the regular "rebase" machinery.
> 
> Such a change to existing behaviour is well within the scope of
> "On-branch topic description support", I would think.