Re: [PATCH 4/5] Head reduction before selecting merge strategy

["Sverre Hvammen Johansen" <hvammen@gmail.com>]

On Fri, Apr 25, 2008 at 3:31 AM, Jakub Narebski <jnareb@gmail.com> wrote:
> "Sverre Hvammen Johansen" <hvammen@gmail.com> writes:
>
>  > See the documentation for an explanation of this feature.
>
>  I think I get the idea now.
>
>  You want to generalize fast-forward merge, or what's equivalent make
>  fast-formard merge to be special case of head reduction.  This should
>  be written both in commit message and in documentation.  Do I
>  understand your goal correctly?
>
>  With head reduction comes three things:
>   * the merge strategy used
>   * recorded parents
>   * generated merge commit message

The recorded parents and the generated merge commit message is the
same with or without this patch.  The only difference is the merge
strategy used.

>  The simplest way would be to use reduced head for all three things,
>  I think.

Actually, we can't do that.  A real merge always need to involve HEAD.
 In the case that HEAD is not included in the reduced parents we could
do a FF+merge, but that is a rather radical change that deserve its
own patch.

Changing the generated merge commit message is also a radical change.

I don't intend to write any patches for this for now.  Maybe later if
the series gets accepted.

>  But I also think that this commit in series is the most controversial
>  one; is it realy needed for other commits?  I would put it then as the
>  last commit in series...

I agree with you, but I don't intend to spend time on this now to
rewrite it again.  I am quite happy with how the series turned out.

>  > +The following shows master and three topic branches.  topicB is based
>  > +on topicA, topicA is previously branched off from master, and topicC
>  > +is based on the tip of the master branch:
>  > +
>  > +------------
>  > +                    o---o---o  topicB
>  > +                   /
>  > +          o---o---o  topicA
>  > +         /
>  > +    o---o---o---o---o---o  master
>  > +                         \
>  > +                          o---o  topicC
>  > +------------
>
>  I think I would start with simpler example without 'topicC', of
>  reduction of octopus to two-parent ordinary merge.

I am not sure that we need to have this in the documentation at all.
I have asked for comments on this before but not received any
feedback.  This late, the documentation will have to be fixed in-tree,
if needed.

>  > diff --git a/git-merge.sh b/git-merge.sh
>  > index 7c34b6c..7c70c56 100755
>  > --- a/git-merge.sh
>  > +++ b/git-merge.sh
>  > @@ -337,11 +337,16 @@ set x $remoteheads ; shift
>  >
>  >  find_reduced_parents "$@"
>  >
>  > -actual_parents=$(git rev-parse "$@")
>
>  This was introduced by some of your earlier commits, isn't it?

Yes,  [PATCH 3/5] Restructure git-merge.sh

-- 
Sverre Hvammen Johansen