Re: Idea for rebase strategy

[Junio C Hamano <junkio@cox.net>]

Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:

> an idea hit me today: maybe we can make rebase work nicely with merges 
> after all. We could record the original branch point and the new branch 
> point for rebases.

One case that that would be simple enough, appear often enough
in real life, and would be useful in practice is this:

       A---B---C---D---E topic
      /       /
  ---X---o---Y---Z master

After forking 'topic' at 'X' and built two commits A and B, the
master has a related change in the area 'topic' works on, and a
merge to adjust is made at C.  Then it builds two other commits
D and E.  We should be able to rebase it on top of the master.

If we have a reliable ref-log for 'topic' that should be trivial
to do.  It will be just the matter of replaying the log on top
of master.  The ref-log says we committed two after we forked,
so we replay them:

       A---B---C---D---E topic
      /       /
  ---X---o---Y---Z master
                  \
                   A'--B'

Then the log says we merged 'Y'.  We faithfully replay that,
which wuold result in "fast-forward -- nothing special is
needed" situation.  The remaining log entries would say we have
two further commits, so replaying them would result in:

       A---B---C---D---E topic
      /       /
  ---X---o---Y---Z master
                  \
                   A'--B'--C'--D' topic'