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Re: Need help merging unrelated histories




On Fri, May 24, 2019 at 9:04 AM Robert Dailey <rcdailey.lists@xxxxxxxxx> wrote:
>
> Everything I'm going to describe is related to this repository:
>
> https://github.com/powervr-graphics/Native_SDK
>
> This repo has several distinct branches. None of them seem to be tied
> to each other. Instead of having a `master` where they branched off
> each of their releases (e.g. 3.1, 3.2, 4.0), it looks like they made a
> copy of previous branches with no ancestry and then continued coding
> on that.
>
> What I'm trying to do is go back and rebase all of the X.X branches
> onto a new `master` branch. I started off with this:
>
> $ git checkout --orphan master
>
> Then I committed a `.gitattributes`. Next, I rebased the first
> (oldest) release branch:
>
> $ git rebase -i --onto master origin/3.0 --root
>
> Then I merged:
>
> $ git checkout master && git merge --no-ff -
>
> Next, I did 3.1:
>
> $ git rebase -i --onto master origin/3.0 origin/3.1 -X theirs
>
> Using interactive mode, Git is smart enough to detect duplicate
> commits and eliminates those, even though the 2 branches do not share
> a merge base. I continued doing this all the way up to rebasing 4.3,
> but that's when things got tough. I see a lot of 'UD', 'UA', 'AU',
> 'AA' merge conflicts. These are obviously due to the fact that the
> branches aren't connected. But I expected was that `-X theirs` would
> always favor what's on the branch being rebased. However, it seems
> this only affects modified conflicts, not adds or deletes.
>
> I was trying to find a way to bulk-resolve these. I mean, if git sees
> a file added on the left AND the right, I want the right one (theirs;
> the one coming from the 4.3 branch). Even though the branches are
> unrelated in terms of their history, I want the net effect of the
> rebase to essentially reflect the files on 4.3 itself. If a file isn't
> present on HEAD, delete it. If a file exists on REBASE_HEAD but not on
> HEAD, then add it. If the same file exists on both, favor the one on
> REBASE_HEAD.
>
> But I don't see a way of doing that. I tried `git checkout --theirs .`
> and `git checkout REBASE_HEAD -- .` but this doesn't work with all
> conflict types.
>
> Can anyone provide some advice on how to properly restructure this
> repository to create some ancestry, as if all along a `master` existed
> and all release branches were based on this in a linear fashion?

By the way, everything I've done so far (up to 4.2) is located here:

https://github.com/rcdailey/Native_SDK

There is a `master` branch in my fork of that repo. I am not sure if
I've done it correctly so far, or if how I've done this up to 4.2
explains why 4.3 is so hard.