[MITgcm-support] closing PR branch without losing subsequent branch (i.e. how to rebase)

[Edward Doddridge]

Hi Dan,

`git rebase master` is the correct command, but there are complications because the history of `branch_remeshing` is somewhat torturous.

The feature branch you are trying to rebase has had `master` merged into it multiple times. Conceptually, rebase moves all the commits from a branch and places them at the end of the branch you are rebasing onto (in this scenario it’s `master`), but your feature branch contains commits where `master` has been merged into the feature branch, which means a straight `rebase` can’t preserve all of the history. I think this is why you are getting the conflicts - they were resolved by merges in the history, but rebasing means those merges are dropped by default.

You might find this Stack Overflow question and answer to be helpful: https://stackoverflow.com/questions/4783599/rebasing-a-git-merge-commit

I’ve never tried rebasing with the ` --preserve-merges` flag, but I think it’s what you need if you want to do this. However, I’m not certain that rebasing is the best idea… You’ve got a complicated git history, with lots of changes and multiple different branches. If it were me, I’d stick with merges and the ugly history, or create a fresh branch and manually transfer the changes to that new branch.

Cheers,
Ed


________________________________
Edward Doddridge
Research Fellow
Australian Antarctic Program Partnership (AAPP)
Institute of Marine and Antarctic Studies (IMAS)
University of Tasmania (UTAS)

www.doddridge.me<http://www.doddridge.me>

On 25 Dec 2019, at 02:55, Daniel Goldberg <dngoldberg at gmail.com<mailto:dngoldberg at gmail.com>> wrote:

Hello All

I had a long outstanding development branch corresponding to a pull request (branch_remeshing), and in the interim i created a branch off of this branch (branch_horiz_remeshing). With J-M's help the initial branch is now merged, so now i have the following:

1) my initial branch (branch_remeshing) is identical to master.
2) my subsequent branch ( branch_horiz_remeshing) is merged with my initial branch.

and I would like it to be as if my branch-of-a-branch was instead a branch of master. from my reading of stackoverflow etc it seems like this should just be a simple call to

git rebase master

while the branch-of-a-branch is checked out, and this should be without issue. However i am getting extensive merge conflicts, even though i have already merged the branches. Is there a better/proper/preferred way to do this?

Apologies for mailing this list rather than one dedicated to git, but a bit of googling seemed to suggest the above, and i would like to adhere to MITgcm best practice anyhow.

Best
Dan
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