Multiple flux instances pointing to the same repo can fail writability check due to shared flux-write-check tag

[maximmold]

Describe the bug
A clear and concise description of what the bug is.

To Reproduce
Steps to reproduce the behaviour:
0. Configure multiple flux instances pointing to the same github repo at different branches

1. When there is latency talking to github, errors are seeing in the logs and the changes to the helm charts cannot be applied.

Expected behavior
Multiple flux instances pointing to the same github repo at different branches shouldn't use the same flux-write-check tag to check writability since the github commands can fail when the tag unexpectedly points to a different commit id.

Logs
flux-write-check -> flux-write-check (cannot lock ref 'refs/tags/flux-write-check': is at 4dbd5cc088259f4e21c7847ca0ea3f2adf62d476 but expected 9043c404310bf76b963b8fb8ddc786e92f9f1c61)\nerror: failed to push some refs to '[email protected]:EPMO/bip-pacman-config.git'\n"

Additional context
Add any other context about the problem here, e.g

• Flux version: 1.15.0