Add FF for configuration file repository property

[mbg]

Follow-up to #3963 which adds a FF to control whether that functionality is enabled or not.

Risk assessment

For internal use only. Please select the risk level of this change:

• Low risk: Changes are fully under feature flags, or have been fully tested and validated in pre-production environments and are highly observable, or are documentation or test only.

Which use cases does this change impact?

Workflow types:

• Advanced setup - Impacts users who have custom CodeQL workflows.
• Managed - Impacts users with dynamic workflows (Default Setup, Code Quality, ...).

Products:

• Code Scanning - The changes impact analyses when analysis-kinds: code-scanning.
• Code Quality - The changes impact analyses when analysis-kinds: code-quality.
• Other first-party - The changes impact other first-party analyses.

Environments:

• Dotcom - Impacts CodeQL workflows on github.com and/or GitHub Enterprise Cloud with Data Residency.

How did/will you validate this change?

• Unit tests - I am depending on unit test coverage (i.e. tests in .test.ts files).

If something goes wrong after this change is released, what are the mitigation and rollback strategies?

• Feature flags - All new or changed code paths can be fully disabled with corresponding feature flags.

How will you know if something goes wrong after this change is released?

• Telemetry - I rely on existing telemetry or have made changes to the telemetry.
  • Dashboards - I will watch relevant dashboards for issues after the release. Consider whether this requires this change to be released at a particular time rather than as part of a regular release.
  • Alerts - New or existing monitors will trip if something goes wrong with this change.

Are there any special considerations for merging or releasing this change?

• No special considerations - This change can be merged at any time.

Merge / deployment checklist

• Confirm this change is backwards compatible with existing workflows.
• Consider adding a changelog entry for this change.
• Confirm the readme and docs have been updated if necessary.

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Pull request overview

This PR introduces a feature flag to control whether the CodeQL Action may read the config-file value from the repository property (added in #3963), allowing that behavior to be enabled/disabled independently of the workflow input.

Changes:

• Add Feature.ConfigFileRepositoryProperty and its configuration (CODEQL_ACTION_CONFIG_FILE_REPOSITORY_PROPERTY) to the feature flag system.
• Gate repository-property-based config file selection behind the new feature flag, while still prioritizing the explicit config-file workflow input.
• Update unit tests for getConfigFileInput to cover both FF-on and FF-off behavior.

Show a summary per file

File	Description
src/init-action.ts	Fetches the new feature flag value and passes it to getConfigFileInput to control repository-property usage.
src/feature-flags.ts	Defines and configures the new ConfigFileRepositoryProperty feature flag and its env var.
src/config/file.ts	Adds a useRepositoryProperty parameter and early-returns when the feature flag is off.
src/config/file.test.ts	Updates existing tests for the new function signature and adds a test verifying FF-off ignores the repository property.
lib/entry-points.js	Generated JS output change (content excluded by policy; not reviewed).

Review details

Files excluded by content exclusion policy (1)

• lib/entry-points.js

• Files reviewed: 4/5 changed files
• Comments generated: 0
• Review effort level: Low

[henrymercer]

Minor: It would be clearer to use an object like { useRepositoryProperty: boolean } here so it's clearer when the function is called what the last argument means.

[mbg]

Agreed with the point, but I expect to change this in line with the changes in #3973 (so that the features are available via the indexed ActionState).