tuf-on-ci-sign fails to install with uv

[joshuagl]

I tried to install tuf-on-ci-sign with uv into a uv created venv and ran into an error:

~ % uv pip install tuf-on-ci-sign
× No solution found when resolving dependencies:
╰─▶ Because there is no version of betterproto==2.0.0b6 and
sigstore-protobuf-specs==0.2.2 depends on betterproto==2.0.0b6, we can
conclude that sigstore-protobuf-specs==0.2.2 cannot be used. (1)
And because only the following versions of sigstore-protobuf-specs are
available:
sigstore-protobuf-specs<=0.2.2
sigstore-protobuf-specs>=0.3.dev0
and sigstore>=2.1.0 depends on sigstore-protobuf-specs>=0.2.2,<0.3.dev0,
we can conclude that sigstore>=2.1.0 cannot be used. (2)

  Because we know from (1) that sigstore-protobuf-specs==0.2.2 cannot
  be used and only the following versions of sigstore-protobuf-specs are
  available:
      sigstore-protobuf-specs<=0.2.2
      sigstore-protobuf-specs>=0.3.dev0
  we can conclude that sigstore-protobuf-specs>=0.2.2,<0.3.dev0 cannot be
  used. (3)

  Because there is no version of betterproto==2.0.0b5 and
  sigstore-protobuf-specs>=0.2.0,<=0.2.1 depends on betterproto==2.0.0b5,
  we can conclude that sigstore-protobuf-specs>=0.2.0,<=0.2.1 cannot be
  used.
  And because we know from (3) that
  sigstore-protobuf-specs>=0.2.2,<0.3.dev0 cannot be used, we can conclude
  that sigstore-protobuf-specs>=0.2.0,<0.3.dev0 cannot be used.
  And because only the following versions of sigstore-protobuf-specs are
  available:
      sigstore-protobuf-specs<=0.2.0
      sigstore-protobuf-specs==0.2.1
      sigstore-protobuf-specs>=0.2.2
  and sigstore>=2.0.0,<=2.0.1 depends on
  sigstore-protobuf-specs>=0.2.0,<0.3.dev0, we can conclude that
  sigstore>=2.0.0,<=2.0.1 cannot be used.
  And because we know from (2) that sigstore>=2.1.0 cannot be used, we can
  conclude that sigstore>=2.0.0 cannot be used.
  And because only the following versions of sigstore are available:
      sigstore<=2.0.0
      sigstore==2.0.1
      sigstore==2.1.0
      sigstore==2.1.2
      sigstore>=3.dev0
  and securesystemslib[sigstore]>=0.30.0 depends on sigstore>=2.0, we can
  conclude that securesystemslib[sigstore]>=0.30.0 cannot be used.
  And because only the following versions of securesystemslib[sigstore]
  are available:
      securesystemslib[sigstore]<=0.30.0
      securesystemslib[sigstore]==0.31.0
      securesystemslib[sigstore]>=1.dev0
  and all versions of tuf-on-ci-sign depend on
  securesystemslib[sigstore]>=0.30, we can conclude that all versions of
  tuf-on-ci-sign cannot be used.
  And because only the following versions of tuf-on-ci-sign are available:
      tuf-on-ci-sign==0.1.0
      tuf-on-ci-sign==0.2.0
      tuf-on-ci-sign==0.3.0
      tuf-on-ci-sign==0.4.0
      tuf-on-ci-sign==0.5.0
      tuf-on-ci-sign==0.6.0
      tuf-on-ci-sign==0.7.0
  and you require tuf-on-ci-sign, we can conclude that the requirements
  are unsatisfiable.

  hint: betterproto was requested with a pre-release marker (e.g.,
  betterproto==2.0.0b6), but pre-releases weren't enabled (try:
  `--prerelease=allow`)

  hint: sigstore-protobuf-specs was requested with a pre-release marker
  (e.g., sigstore-protobuf-specs>0.2.2,<0.3.dev0), but pre-releases
  weren't enabled (try: `--prerelease=allow`)

  hint: sigstore was requested with a pre-release marker (e.g., any of:
      sigstore>2.0.0,<2.0.1
      sigstore>2.0.1,<2.1.0
      sigstore>2.1.0,<2.1.2
      sigstore>2.1.2,<3.dev0
  ), but pre-releases weren't enabled (try: `--prerelease=allow`)

  hint: securesystemslib[sigstore] was requested with a pre-release marker
  (e.g., any of:
      securesystemslib[sigstore]>0.30.0,<0.31.0
      securesystemslib[sigstore]>0.31.0,<1.dev0
  ), but pre-releases weren't enabled (try: `--prerelease=allow`)

[jku]

https://github.com/sigstore/protobuf-specs/blob/main/gen/pb-python/pyproject.toml#L28C18-L28C38

Looks like pip is fine with installing a beta release when protobuf-specs explicitly depends on it but uv is not cool with it. Not sure what uv needs --prerelease=allow for when the dependency is a specific version. But I also recognise that prereleases are a nightmare so probably no decision is good for every case:

Pre-releases are notoriously difficult to model, and are a frequent source of bugs in other packaging tools. uv's pre-release handling is intentionally limited and intentionally requires user intervention to opt in to pre-releases to ensure correctness, though pre-release handling will be revisited in future releases.

Based on the readme it might also work if we explicitly depended on betterproto>=2.0.0b6 but that feels like a hack to