Running prek auto-update changes a pinned rev for lycheeverse/lychee from a stable tag to the mutable branch nightly, and then prints a warning that mutable rev values are unsupported and will not be updated after first install. This upgrade target seems wrong because it replaces a stable pin with a mutable reference.

Reproduction

1. .pre-commit-config.yaml:

• repo: https://github.com/lycheeverse/lychee
  rev: lychee-v0.22.0

2. Run: prek auto-update

• repo: https://github.com/lycheeverse/lychee
  rev: nightly

Warning:

warning: The following repos have mutable rev fields (moving tag / branch):
https://github.com/lycheeverse/lychee: nightly
Mutable references are never updated after first install and are not supported.
See https://pre-commit.com/#using-the-latest-version-for-a-repository for more details.
Hint: prek autoupdate often fixes this

Expected Result:

prek auto-update should not replace a pinned tag/commit with a mutable rev like nightly. It should prefer the latest stable tag.