Re: [PATCH 1/1] Add --first-parent support to interactive rebase.

From: Björn Steinbrink <b.steinbrink@gmx.de>
Date: Oct 31, 2007, 05:53 UTC
Message-ID: <20071031055303.GB3326@atjola.homenet>
In-Reply-To: <7vodefj2lk.fsf@gitster.siamese.dyndns.org>

On 2007.10.30 22:05:27 -0700, Junio C Hamano wrote:

> Your MUA seems to mark the UTF-8 message you are sending out as
> 8859-1, which means your name in the message gets corrupt.

Hm, that would be git-send-email then, anything I need to configure? (Actually I don't see it marking the message as anything)

Show 13 quoted lines

> Björn Steinbrink <B.Steinbrink@gmx.de> writes:
> 
> > By default, rebase will take all commits from the branch that is to be
> > rebased which are missing in upstream. The new --first-parent option
> > allows to just follow the first parent and thus completely ignore
> > merges.
> >
> > Additionally, when used together with --preserve-merges (which is the
> > more useful use-case) it will no longer rebase the commits from the
> > merged-in branches, but instead redo the merge with the original
> > parents.
> >
> > That means that:

Given this situation:

> >      ---H------I topicB
> >     /    \      \
> > ...
> > does no longer become:

Which results in:

Show 7 quoted lines

> >                 -H'--------I'
> >                /  \         \
> >               D'---E'---F'---G' topicA
> >              /
> >     A---B---C master
> >      \
> >       H---I topicB

When you do "git-rebase -p -i master topicA"

You can now also get:

> >     A---B---C master
> > ...
> >         ---------H---------I topicB

When you do "git-rebase -p -i --first-parent master topicA"

That's better, right?

Show 8 quoted lines

> And crucially, you forgot to say "... when you do X".
> 
> I am assuming that you meant:
> 
>     This (picture) becomes this (picture) instead of this (picture)
>     when you run "git rebase -p -m master topicA".
> 
> but without it, the nice ASCII drawings loses their value.

:-/

> It is somewhat disturbing that this treats the first parent too
> special.

The original use-case for the "-p -i --first-parent" case was a question on #git, where someone had sth. like this:

   o---o---o---o---o remote/branch
        \           \
     o---o---o---o---o topicA
    /
   o---o---o master trunk

Now that guy was using git-svn to dcommit into svn from master. To dcommit the changes from topicA he had to have that based on master, and he wanted to preserve the merges from remote/branch to have them squashed when dcommitted to svn. So what he wanted was:

     ...---o---o---o---o---o remote/branch
                \           \
             o---o---o---o---o topicA
            /
   o---o---o master trunk

The default behaviour of rebase would totally flat out the history and instead of two sqaush merges (which he wanted), svn would've seen a huge amount of commits comning from remote/branch. And the plain -p behaviour would have duplicated all those branches from remote/branch for no good reason, so I came up with that --first-parent thing.

Better ideas are welcome, I just don't know git well enough to come up with anything better...

Thanks, Björn