dolt push may be overly aggressive in its fast-forward check.

[reltuk]

Dolt push currently runs a fast-forward branch check against the local tracking reference to the remote branch before it goes ahead with the push attempt. This means that if the local tracking reference is stale, you can get a failure. This can really come up if the remote branch has been deleted.

For example, consider the following:

First, make a remote with a main and an alt branch, with your repo tracking both:

mkdir repo
cd repo
dolt init
dolt remote add origin file://../remote
dolt push origin main:main
dolt checkout -b alt
dolt commit -m new --allow-empty
dolt push origin alt:alt

Then, merge the alt branch to main, push it to main, and delete the alt branch from the remote:

cd ..
dolt clone file://remote cloned
cd cloned
dolt merge origin/alt
dolt push origin main:main
dolt push origin :alt

Then go back to the original repo, create a new branch alt HEAD off of main, and attempt to push that to the remote alt:

cd ../repo
dolt checkout main
dolt checkout -B alt
dolt commit -m another --allow-empty
dolt push origin alt:alt

At that point, you will get a rejected push:

- Uploading...To file:///Users/aaronson/DoltPushBug/remote
 ! [rejected]            alt -> alt (non-fast-forward)
error: failed to push some refs to 'file:///Users/aaronson/DoltPushBug/remote'
hint: Updates were rejected because the tip of your current branch is behind
hint: its remote counterpart. Integrate the remote changes (e.g.
hint: 'dolt pull ...') before pushing again.

Ways to fix include:

dolt push -f alt:alt

or running

dolt fetch -p origin

before you push.

It's not clear to me to what degree we should be using the local tracking branch state for this fast-forward check.

[reltuk]

Fixed in #7450