Re: merge maintaining history

[Junio C Hamano <gitster@pobox.com>]

"David J. Bakeman" <nakuru@comcast.net> writes:

>> So you want to merge the "new" history into the original tree now, so
>> you checkout the original tree, then "git merge <new-remote>/<branch>"
>> and then fix up any conflicts, and then git commit to create a merge
>> commit that has the new history. Then you could push that to both
>> trees.
>>
>> I would want a bit more information about your setup before providing
>> actual commands.
>
> Thanks I think that's close but it's a little more complicated I think
> :<(  I don't know if this diagram will work but lets try.
>
> original A->B->C->D->E->F
>              \
> first branch  b->c->d->e
>
> new repo e->f->g->h
>
> Now I need to merge h to F without loosing b through h hopefully.  Yes e
> was never merged back to the original repo and it's essentially gone now
> so I can't just merge to F or can I?

With the picture, I think you mean 'b' is forked from 'B' and the
first branch built 3 more commits on top, leading to 'e'.

You say "new repo" has 'e' thru 'h', and I take it to mean you
started developing on top of the history that leads to 'e' you built
in the first branch, and "new repo" has the resulting history that
leads to 'h'.

Unless you did something exotic and non-standard, commit 'e' in "new
repo" would be exactly the same as 'e' sitting on the tip of the
"first branch", so the picture would be more like:

> original A->B->C->D->E->F
>              \
> first branch  b->c->d->e
>                         \
> new repo                 f->g->h

no?  Then merging 'h' into 'F' will pull everything you did since
you diverged from the history that leads to 'F', resulting in a
history of this shape:

> original A->B->C->D->E->F----------M
>              \                    /
> first branch  b->c->d->e         /
>                         \       /
> new repo                 f->g->h

If on the other hand you did something non-standard and exotic to
rewrite 'e' at the end of "first branch" and make a different commit
that does not even have any parent in "new repo", and the history of
"new repo" originates in such a commit that is not 'e', things will
become messy.  But I didn't think I read you did anything unusual so
a simple "git checkout F && git merge h" should give you what you
want.