flatten-merge history

flatten-merge history

[Henning Moll]

Hi,

suppose the following history

     P - - - Q - - - - - R       <-extern

A -- - B - - - C - D - - - E   <-master
          \           \
           M ...       \         <-b1
                        \
                         W ...   <-b2


Note that master and extern do not have a common parent. Both histories 
are 'distinct', they do not share common files, so there can't be any 
merge conflicts. What i want to achieve is this history:

     P - - - Q - - - - - R       <-extern

A -P'- B'- Q'- C'- D'- R'- E'  <-master
          \           \
           M'...       \         <-b1
                        \
                         W'...   <-b2

The two histories should be merged in chronological order.
So while master reflects P-Q-R, b2 should only reflect P-Q and b1 should 
only reflect P.

All my current attempts (surgery with git replace or interactive rebase 
combined with merging) were not successfull.

Any ideas?

Best regards
Henning

Re: flatten-merge history

[Christian Couder]

Hi,

On Sat, Oct 25, 2014 at 2:31 PM, Henning Moll <newsScott@gmx.de> wrote:
> Hi,
>
> suppose the following history
>
>     P - - - Q - - - - - R       <-extern
>
> A -- - B - - - C - D - - - E   <-master
>           \           \
>           M ...       \         <-b1
>                           \
>                           W ...   <-b2
>
>
> Note that master and extern do not have a common parent. Both histories are
> 'distinct', they do not share common files, so there can't be any merge
> conflicts. What i want to achieve is this history:
>
>     P - - - Q - - - - - R       <-extern
>
> A -P'- B'- Q'- C'- D'- R'- E'  <-master
>             \           \
>             M'...       \         <-b1
>                             \
>                             W'...   <-b2
>
> The two histories should be merged in chronological order.
> So while master reflects P-Q-R, b2 should only reflect P-Q and b1 should
> only reflect P.
>
> All my current attempts (surgery with git replace or interactive rebase
> combined with merging) were not successfull.

Could you tell us why interactive rebase did not work?
If there can't be any merge conflict between both histories, it should
have worked without asking you to resolve any conflict.

Best,
Christian.

Re: flatten-merge history

[Henning Moll]

Am 26.10.2014 um 06:46 schrieb Christian Couder:
> Hi,Could you tell us why interactive rebase did not work?

First of all i have to admit that i did not i-rebase-merge, but 
i-rebase-cherrypick. Now i tried it with i-rebase-merge and it didn't 
work either.
Here's my workflow, which i repeated for all commits of 'extern' (in 
chronological order'). For simplicity let's assume that there is a 
parent commit for 'A'

1. For P, A is the nearest prior commit on 'master'
2. on master: git rebase -i A^
3. change A from pick to edit. save. quit
4. git merge P
5. git rebase --continue

 From the perspective of 'master' this worked. But as all of the commits 
have been rewritten, the branches b1 and b2 no longer refer to 'master'. 
Branch b2, for example, still branches off at B and not B'. So after 
this action, my history looks like this:


     P - - - Q - - - - - R       <-extern
       \
A'- m - B'- - - C'- D'- - - E'  <-master

A - - - B - - - C - D
          \           \
           M ...       \         <-b1
                        \
                         W ...   <-b2

A and A' are nearly the same: they only differ in the new 
GIT_COMITTER_DATE.
Now this is what i try to get (after only applying P):



     P - - - Q - - - - - R       <-extern
     \
A'- m - B'- - - C'- D'- - - E'  <-master
          \           \
           M'...       \         <-b1
                        \
                         W'...   <-b2

Regards
Henning

Re: flatten-merge history

[Andreas Schwab]

Henning Moll <newsScott@gmx.de> writes:

> 1. For P, A is the nearest prior commit on 'master'
> 2. on master: git rebase -i A^
> 3. change A from pick to edit. save. quit
> 4. git merge P
> 5. git rebase --continue
>
> From the perspective of 'master' this worked. But as all of the commits
> have been rewritten, the branches b1 and b2 no longer refer to
> 'master'. Branch b2, for example, still branches off at B and not B'.

You only rebased master, so b1 and b2 were unchanged.  If you want to
change b1 and b2 you have to rebase them as well.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: flatten-merge history

[Christian Couder]

On Sun, Oct 26, 2014 at 4:19 PM, Andreas Schwab <schwab@linux-m68k.org> wrote:
> Henning Moll <newsScott@gmx.de> writes:
>
>> 1. For P, A is the nearest prior commit on 'master'
>> 2. on master: git rebase -i A^
>> 3. change A from pick to edit. save. quit
>> 4. git merge P
>> 5. git rebase --continue
>>
>> From the perspective of 'master' this worked. But as all of the commits
>> have been rewritten, the branches b1 and b2 no longer refer to
>> 'master'. Branch b2, for example, still branches off at B and not B'.
>
> You only rebased master, so b1 and b2 were unchanged.  If you want to
> change b1 and b2 you have to rebase them as well.

Yeah. Henning, when interactively rebasing, in our editor, you should
have something like:

pick A
pick P
pick B
pick Q
pick C
pick D
pick R
pick E

which should work without any conflict.
And then you can rebase the b1 and b2 branches on the resulting branch.

Best,
Christian.

Re: flatten-merge history

[Henning Moll]

Am 26.10.2014 um 20:02 schrieb Christian Couder:
> Yeah. Henning, when interactively rebasing, in our editor, you should 
> have something like: pick A pick P pick B pick Q pick C pick D pick R 
> pick E which should work without any conflict. And then you can rebase 
> the b1 and b2 branches on the resulting branch.

Thank you all very much. It worked!

I didn't know that i could also introduce new commits in the interactive 
rebase list. Just for the record, in case others need to do such a task:

intial situation:

     P - - - Q - - - - - R       <-extern

A - - - B - - - C - D - - - E   <-master
          \           \
           M ...       \         <-b1
                        \
                         W ...   <-b2

On master:
$ git rebase -i --root

(editor opens showing

pick A
pick B
pick C
pick D
pick E

modify this to

pick A
pick P
pick B
pick Q
pick C
pick D
pick R
pick E

save, quit. Now, master is already fixed. Now fix the branches:

$ git rebase --onto B' B b1
$ git rebase --onto D' D b2

Just a final question: Is it possible to keep the GIT_COMMITTER_DATE in 
all those rebases?

Thanks again
Henning

Re: flatten-merge history

[Andreas Schwab]

Henning Moll <newsScott@gmx.de> writes:

> Just a final question: Is it possible to keep the GIT_COMMITTER_DATE in
> all those rebases?

If you want that you need to work with git filter-branch.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."