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Find successor of common ancestor

Subject: Find successor of common ancestor

## tl;dr

7 messages between Jul 16, 2010 and Jul 16, 2010.

replies: 6people: 5as markdown or json

Enrico Weigelt· Jul 16, 2010, 08:29 UTC · lore
Hi folks,
suppose the following situation:

I've forked some branch A into B, now A and B have evolved independently for quite some time into A' and B'. Now I'd like to rebase B' along A' history line step by step - first on A+1, then A+3, ... until A' (that's what I'd call zip-rebase).

For this I need to find out the successor commit A (along the A' history line). Does anyone know how to do that ?

cu
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----------------------------------------------------------------------
 Enrico Weigelt, metux IT service -- http://www.metux.de/

 phone:  +49 36207 519931  email: weigelt@metux.de
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Santi Béjar· Jul 16, 2010, 08:49 UTC · re: Enrico Weigelt · lore

Re: Find successor of common ancestor

On Fri, Jul 16, 2010 at 10:29 AM, Enrico Weigelt <weigelt@metux.de> wrote:
Show 10 quoted lines
>
> Hi folks,
>
>
> suppose the following situation:
>
> I've forked some branch A into B, now A and B have evolved
> independently for quite some time into A' and B'. Now I'd like
> to rebase B' along A' history line step by step - first on A+1,
> then A+3, ... until A' (that's what I'd call zip-rebase).
This is just what "git rebase"  does:

$ git checkout B' $ git rebase A'

HTH, Santi

Enrico Weigelt· Jul 16, 2010, 09:06 UTC · re: Santi Béjar · lore

Re: Find successor of common ancestor

* Santi Béjar <santi@agolina.net> wrote:
Show 16 quoted lines
> On Fri, Jul 16, 2010 at 10:29 AM, Enrico Weigelt <weigelt@metux.de> wrote:
> >
> > Hi folks,
> >
> >
> > suppose the following situation:
> >
> > I've forked some branch A into B, now A and B have evolved
> > independently for quite some time into A' and B'. Now I'd like
> > to rebase B' along A' history line step by step - first on A+1,
> > then A+3, ... until A' (that's what I'd call zip-rebase).
> 
> This is just what "git rebase"  does:
> 
> $ git checkout B'
> $ git rebase A'
Yes, but I need to find out A+1 for my zip-rebase.
cu
-- 
----------------------------------------------------------------------
 Enrico Weigelt, metux IT service -- http://www.metux.de/

 phone:  +49 36207 519931  email: weigelt@metux.de
 mobile: +49 151 27565287  icq:   210169427         skype: nekrad666
----------------------------------------------------------------------
 Embedded-Linux / Portierung / Opensource-QM / Verteilte Systeme
----------------------------------------------------------------------
Johan Herland· Jul 16, 2010, 12:19 UTC · re: Enrico Weigelt · lore

Re: Find successor of common ancestor

On Friday 16 July 2010, Enrico Weigelt wrote:
> * Santi Béjar <santi@agolina.net> wrote:
> > On Fri, Jul 16, 2010 at 10:29 AM, Enrico Weigelt <weigelt@metux.de> 
wrote:
Show 16 quoted lines
> > > Hi folks,
> > >
> > >
> > > suppose the following situation:
> > >
> > > I've forked some branch A into B, now A and B have evolved
> > > independently for quite some time into A' and B'. Now I'd like
> > > to rebase B' along A' history line step by step - first on A+1,
> > > then A+3, ... until A' (that's what I'd call zip-rebase).
> >
> > This is just what "git rebase"  does:
> >
> > $ git checkout B'
> > $ git rebase A'
>
> Yes, but I need to find out A+1 for my zip-rebase.
IINM you have the following situation
A0---A1---A2---A3---A4  <-- A'
  \
   B1---B2---B3--B4  <-- B'

...and you want to rebase B' (i.e. B1 through B4), first onto A1, then onto A2, the onto A3, and finally onto A4. I have no idea WHY you would want to do this (rebasing directly onto A4 (like Santi suggests) is much cheaper), but you can certainly coax Git into doing it, anyway.

To list commits A1, A2, A3, A4 (in that order), do:
  git rev-list --reverse B'..A'
You can now loop over the results like this:
  git checkout B'
  for a in $(git rev-list --reverse ..A'); do
      git rebase $a
  done
Hope this helps,
...Johan
-- 
Johan Herland, <johan@herland.net>
www.herland.net
Enrico Weigelt· Jul 16, 2010, 15:35 UTC · re: Johan Herland · lore

Re: Find successor of common ancestor

* Johan Herland <johan@herland.net> wrote:
Show 10 quoted lines
> IINM you have the following situation
> 
> A0---A1---A2---A3---A4  <-- A'
>   \
>    B1---B2---B3--B4  <-- B'
> 
> ...and you want to rebase B' (i.e. B1 through B4), first onto A1, then 
> onto A2, the onto A3, and finally onto A4. I have no idea WHY you would 
> want to do this (rebasing directly onto A4 (like Santi suggests) is 
> much cheaper), but you can certainly coax Git into doing it, anyway.

If the branches go off too far, you can easily end up in a lot of unresolvable conflicts, while on zip-rebase, there's great chance that 3way-merge will catch this.

Show 10 quoted lines
> To list commits A1, A2, A3, A4 (in that order), do:
> 
>   git rev-list --reverse B'..A'
> 
> You can now loop over the results like this:
> 
>   git checkout B'
>   for a in $(git rev-list --reverse ..A'); do
>       git rebase $a
>   done
Thx, I'll have a try :)
cu
-- 
----------------------------------------------------------------------
 Enrico Weigelt, metux IT service -- http://www.metux.de/

 phone:  +49 36207 519931  email: weigelt@metux.de
 mobile: +49 151 27565287  icq:   210169427         skype: nekrad666
----------------------------------------------------------------------
 Embedded-Linux / Portierung / Opensource-QM / Verteilte Systeme
----------------------------------------------------------------------
Andreas Schwab· Jul 16, 2010, 12:29 UTC · re: Enrico Weigelt · lore

Re: Find successor of common ancestor

Enrico Weigelt <weigelt@metux.de> writes:
Show 19 quoted lines
> * Santi Béjar <santi@agolina.net> wrote:
>> On Fri, Jul 16, 2010 at 10:29 AM, Enrico Weigelt <weigelt@metux.de> wrote:
>> >
>> > Hi folks,
>> >
>> >
>> > suppose the following situation:
>> >
>> > I've forked some branch A into B, now A and B have evolved
>> > independently for quite some time into A' and B'. Now I'd like
>> > to rebase B' along A' history line step by step - first on A+1,
>> > then A+3, ... until A' (that's what I'd call zip-rebase).
>> 
>> This is just what "git rebase"  does:
>> 
>> $ git checkout B'
>> $ git rebase A'
>
> Yes, but I need to find out A+1 for my zip-rebase.

git rev-list [--first-parent] A..A' | tac | while read rev; do git rebase $rev; done

Andreas.
-- 
Andreas Schwab, schwab@linux-m68k.org
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"And now for something completely different."
Avery Pennarun· Jul 16, 2010, 15:44 UTC · re: Enrico Weigelt · lore

Re: Find successor of common ancestor

On Fri, Jul 16, 2010 at 4:29 AM, Enrico Weigelt <weigelt@metux.de> wrote:
> I've forked some branch A into B, now A and B have evolved
> independently for quite some time into A' and B'. Now I'd like
> to rebase B' along A' history line step by step - first on A+1,
> then A+3, ... until A' (that's what I'd call zip-rebase).

You haven't *really* explained what you want to do here, but that doesn't really effect the answer to your actual question...

> For this I need to find out the successor commit A (along the A'
> history line). Does anyone know how to do that ?
git rev-list --first-parent --reverse $(git merge-base A B)..A
Have fun,
Avery

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