Can't, because a commit's hash takes into account the parent hashes.
Haven't used --update-refs, but reading it, it should result in your third graph. So,
> is there a way to get `git rebase` to have the same behavior?
is already the case.
I don't think it does. I tried locally:
mkdir test; cd test; git init
touch a; git add a; git commit -m 'a'
touch b; git add b; git commit -m 'b'
touch c; git add c; git commit -m 'c'
git checkout -b branched-feature HEAD~
touch d; git add d; git commit -m 'd'
git checkout main
echo 'change' > b; git add b; git commit -m 'fix b'
git rebase -i --root --update-refs
* commit (HEAD -> main)
|
| c
|
* commit
|
| b
|
| * commit (branched-feature)
| |
| | d
| |
| * commit
|/
| b
|
* commit
a
* commit (branched-feature)
|
| d
|
| * commit (HEAD -> main)
|/
| c
|
* commit
|
| b
|
* commit
aEDIT: Yeah, this seems to be it. `git branch b` on b, then `git rebase -i --update-ref @~3` from main caused branch ref `b` to move from d86229e to 02fcaf7:
* 1e354fb (HEAD -> main) fix b
* 40e6f70 c
* 02fcaf7 (b) b
| * f4188e0 (branched-feature) d
| * d86229e b
|/
* 5fe78fa aAdd --oneline to get the compact version from the other reply.
Which is usually not what you want; most of the time you want E', which is E reparented onto B'. But sometimes you want E to remain untouched and stay parented on the original B. Depends on the situation.