Add resolution-strategy input to support oldest compatible version selection

[Copilot]

Adds a new resolution-strategy input that allows users to choose between installing the highest (default) or lowest compatible version when resolving version ranges.

Closes: #620

Problem

When specifying version constraints like >=0.4.0, setup-uv would always install the latest compatible version. This made it difficult to test against the minimum supported uv version to catch compatibility issues early, similar to how uv --resolution-strategy lowest works.

Solution

This PR introduces a new resolution-strategy input with two options:

• "highest" (default): Install the latest version that satisfies constraints - maintains existing behavior
• "lowest": Install the oldest version that satisfies constraints - new functionality

Usage Examples

Test with minimum supported version:

- name: Install oldest compatible uv version
  uses: astral-sh/setup-uv@v6
  with:
    version: ">=0.4.0"
    resolution-strategy: "lowest"

Matrix testing with both strategies:

strategy:
  matrix:
    resolution-strategy: ["highest", "lowest"]
steps:
  - uses: astral-sh/setup-uv@v6
    with:
      version: ">=0.4.0"
      resolution-strategy: ${{ matrix.resolution-strategy }}
      cache-suffix: ${{ matrix.resolution-strategy }}

Implementation Details

• Input validation: Validates strategy values with clear error messages
• Version resolution: Extended resolveVersion() to support both semver and PEP 440 specifications using minSatisfying/maxSatisfying functions
• Backward compatibility: Existing workflows continue working unchanged
• Documentation: Updated README with usage examples and FAQ section reference

Testing

• Extended the test-specific-version job in .github/workflows/test.yml with matrix testing for both resolution strategies
• Added test cases using version ranges like >=0.4.25,<0.5 and >=0.1.0,<0.2 to verify both highest and lowest resolution behavior
• Integration testing validates the feature works correctly with real version resolution scenarios

This enables users to test their configurations against the minimum supported uv version, helping catch cases where newer uv features are required than declared in version constraints.

Fixes #620

Original prompt

Implemented the changes requested in @astral-sh/setup-uv/issues/620

Add a new input resolution-strategy. The default is "highest" the other supported option is "lowest"

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[eifinger]

@copilot remove all the unit tests you added in the __tests__ folder. They are not testing any code and are thus useless.

Extend the test test-specific-version in .github/workflows/test.yml instead. Add an additional input in the matrix for the resolution strategy. Look in version-manifest.json for available versions

[Copilot]

@copilot remove all the unit tests you added in the __tests__ folder. They are not testing any code and are thus useless.

Extend the test test-specific-version in .github/workflows/test.yml i...

Removed all unit tests from __tests__ folder and extended the test-specific-version job with resolution strategy matrix testing. Added test cases for both highest and lowest strategies using version ranges like >=0.4.25,<0.5 and >=0.1.0,<0.2 to verify the resolution behavior works correctly. Commit: a7a9e23