Re: If a branch moves a submodule, "merge --ff[-only]" succeeds while "merge --no-ff" fails with conflicts

From: Dakota Hawkins <dakotahawkins@gmail.com>
Date: Sep 6, 2016, 18:40 UTC
Message-ID: <CAG0BQX=i6gcA0ba5T7vcnaDPucZDcTOZUEGr=fhgpcDrbvQ1+g@mail.gmail.com>
In-Reply-To: <CAG0BQX=wvpkJ=PQWV-NbmhuPV8yzvd_KYKzJmsfWq9xStZ2bnQ@mail.gmail.com>

Is there any additional information I could provide that would be helpful?

Dakota

On Fri, Sep 2, 2016 at 3:22 PM, Dakota Hawkins <dakotahawkins@gmail.com> wrote:

Show 55 quoted lines

> Below is a simple reproduction of the issue.
>
> The _real_ problem is that this is how our pull request merges work,
> they're not allowed to do fast-forward merges. To work around this we
> are having to split this up into two pull requests/merges: One that
> copies the submodules to the new location and includes any fixes
> required to support the move, and a second that removes the old
> locations.
>
> ## Setup steps
> git clone https://github.com/dakotahawkins/submodule-move-merge-bug-main-repo.git
> cd submodule-move-merge-bug-main-repo
>     ## How it was initially constructed
>     # git submodule add ../submodule-move-merge-bug-submodule-repo.git
> ./submodule-location-1
>     # git commit -m "Added submodule in its initial location"
>     # git push
>     # git checkout -b move-submodule
>     # git mv ./submodule-location-1 ./submodule-location-2
>     # git commit -m "Moved submodule"
>     # git push --set-upstream origin move-submodule
> git branch move-submodule origin/move-submodule
>
> ## Test fast-forward merge, this will work
> git checkout -b merge-ff-test master # warning: unable to rmdir
> submodule-location-2: Directory not empty
> rm -rf ./submodule-location-2
> git merge --ff-only move-submodule
>
> ## Test no-fast-forward merge, this will fail with conflicts:
> git checkout -b merge-no-ff-test master
> git merge --no-ff move-submodule
>     # Auto-merging submodule-location-2
>     # Adding as submodule-location-2~move-submodule instead
>     # Automatic merge failed; fix conflicts and then commit the result.
> git status
>     # On branch merge-no-ff-test
>     # You have unmerged paths.
>     #   (fix conflicts and run "git commit")
>     #   (use "git merge --abort" to abort the merge)
>     #
>     # Changes to be committed:
>     #
>     #         modified:   .gitmodules
>     #         deleted:    submodule-location-1
>     #
>     # Unmerged paths:
>     #   (use "git add <file>..." to mark resolution)
>     #
>     #         added by us:     submodule-location-2
>     #
>     # fatal: Not a git repository: 'submodule-location-1/.git'
>     # Submodule changes to be committed:
>     #
>     # * submodule-location-1 07fec24...0000000: