Re: how to rebase backwards

["David Kågedal" <davidk@lysator.liu.se>]

bill lam <cbill.lam@gmail.com> writes:

> Thank you for detail explanation.  From what you described, I begin
> with master commit D, 
>  $ git checkout -b deploy
>  $ git commit --allow-empty -m deploy

But why on earth would you want to use --allow-empty? There is no reason
for that. Just let deploy be where it is when you created it (until you
actually add something to it).

>                       E
>                      /^ deploy
>      ---A---B---C---D
>                     ^ master
>  
>  $ git rebase -i A
>
>                       v deploy
>           B'--C'--D'--E'
>          /
>      ---A---B---C---D
>                     ^ master
>
> since E is an empty commit, I suppose content of D' E' and D are
> identical at this point.  Is that correct?

Assuming you didn't intentionally change it during rebase, yes.

> If several months later, I forget which is the common ancestor for
> master and deploy, how do I generate the above graph or identify
> commit A as the common ancestor for these two branches?

That is exactly what git does all the time. You can use many
command. For instance git log --graph master...deply whill show you both
branches, starting from their common ancestor. "git merge-base deploy
master" will tell you that the common ancestor is. Etc.

-- 
David Kågedal