Re: merge maintaining history

W dniu 19.01.2017 o 22:42, Junio C Hamano pisze:

"David J. Bakeman" [off-list ref] writes:

 
[...]

quoted

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:

quoted

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

no?

On the other hand Git has you covered even if you did something 
non-standard, like starting new repo from the _state_ of 'e', that
is you have just copied files and created new repository, having
'e' (or actually 'e*') as an initial commit.

   original A<-B<-C<-D<-E<-F
                \
   first branch  b<-c<-d<-e

   new repo               e*<-f<-g<-h

Note that arrows are in reverse direction, as it is newer commit
pointing to its parents, not vice versa.

Assuming that you have everything in a single repository, by adding
both original and new repo as "remotes", you can use 'git replace'
command to replace 'e*' with 'e'.

   original A<-B<-C<-D<-E<-F
                \
   first branch  b<-c<-d<-e
                           \
   new repo                 \-f<-g<-h
   (with refs/replace)

    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:

quoted

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

Then you would have the above history in repositories that fetched
refs/replace/*, and the one below if replacement info is absent:

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

But as Junio said it is highly unlikely that you are in this situation.

HTH
-- 
Jakub Narębski