issue: fetch will give a fatal error once when a new arbitrary branch on 
the remote contains a submodule url change with updated sha

This was an issue I originally opened on git-for-windows a while back. 
(https://github.com/git-for-windows/git/issues/3404)

But it's actually reproducible on Linux

Seems to be a regression since I could not repro on version 1.9

Issue still present on version 2.45.0.31.gd4cc1ec35f

Local repro steps (complete test script attached)
- create repo A with a commit on master
- create repo B with a commit on master
- create repo X and add a submodule S1 pointing to A, commit to master.
- clone repo X with submodules to repo Z
- in repo X, create branch X1 from master. Change submodule S1 url to 
repo B and commit on X1.
- in repo Z, fetch and notice the fatal error "upload-pack: not our ref SHA"

 From there, you can then quickly repro the error like so:
- in repo Z , delete branch origin/X1 and then fetch again.

Current workaround is to set submodule.recurse to false

-- 

Martin