fix: filter unsupported cooldown options

[zkoppert]

Pull Request

Proposed Changes

I found that Evergreen currently adds three unsupported SemVer cooldown fields to generated GitHub Actions configuration, which can make the Dependabot configuration invalid. I now filter semver-major-days, semver-minor-days, and semver-patch-days based on each ecosystem's documented capabilities. I preserve default-days, include, and exclude when at least one supported day field remains.

I also omit the cooldown block when filtering leaves no supported day field. This fixes #605 and applies the same capability check to all 29 ecosystems Evergreen currently detects.

Ecosystem	Before	After
github-actions	default-days plus three unsupported semver-*-days fields	default-days remains and the three unsupported fields are omitted
npm	All configured cooldown fields	All configured cooldown fields remain unchanged
github-actions with SemVer-only input	A cooldown block containing unsupported fields and exclude	No cooldown block because no supported day field remains

I chose a centralized capability set instead of special-casing GitHub Actions so every generated ecosystem follows the same rule. The tradeoff is that newly supported ecosystems must be added to the set before Evergreen emits their SemVer-specific cooldown fields.

Testing

• I ran make test in the fresh evergreen-605-validation Codespace at commit 319a8e8, covering 182 tests with 100% line coverage.
• I added regression tests for mixed npm and GitHub Actions configuration, non-SemVer ecosystems, and SemVer-only cooldown input.

Rollout

No migration or feature flag is required because the fix only changes newly generated Dependabot YAML. After merge, I will watch for reports of invalid generated configuration and confirm GitHub Actions entries no longer contain unsupported SemVer cooldown fields.

Readiness Checklist

Author/Contributor

• Documentation is not needed because the supported input format is unchanged.
• I ran make lint and fixed all introduced issues.
• I ran make test and added coverage for the new behavior.

[Copilot]

Copilot review overview

🟢 Approval recommended

The change is narrowly scoped, behavior is covered by targeted regression tests, and the updated generation logic matches the PR’s stated acceptance criteria.

Review tier: Lite
Findings: None

What changed in this PR

This PR fixes invalid generated dependabot.yml output by filtering out unsupported SemVer-specific cooldown keys (semver-*-days) for ecosystems that don’t support them, while retaining supported cooldown fields (like default-days, plus include/exclude when applicable). It centralizes ecosystem capability checks so the same rules apply consistently across all detected ecosystems, including a regression fix for github-actions (Issue #605).

Changes:

• Introduces a SEMVER_COOLDOWN_ECOSYSTEMS allowlist and filters SemVer cooldown keys per-ecosystem during config generation.
• Omits the cooldown block entirely when filtering removes all supported day fields for an ecosystem.
• Adds/updates unit tests covering mixed ecosystem output, GitHub Actions filtering, and SemVer-only cooldown inputs.

File	Description
dependabot_file.py	Adds SemVer cooldown capability filtering and omits unsupported/empty cooldown blocks per ecosystem.
test_dependabot_file.py	Adds regression tests to ensure unsupported SemVer cooldown keys are filtered (and cooldown omitted when empty).

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