feat: add node-version-file input for reading Node.js version from files

[fengmk2]

Support reading Node.js version from .nvmrc, .node-version, .tool-versions, and package.json (devEngines.runtime then engines.node), matching actions/setup-node behavior. Ignored when node-version is set.

Also extracts resolveWorkspacePath utility to reduce duplication.

[Copilot]

Pull request overview

Adds support for resolving a Node.js version from common “version files” (similar to actions/setup-node) via a new node-version-file input, and centralizes workspace path resolution to reduce duplication.

Changes:

• Add node-version-file input (action.yml + inputs parsing/types) and use it in the main action flow when node-version is not provided.
• Introduce resolveNodeVersionFile() with support for .nvmrc, .node-version, .tool-versions, and package.json, with accompanying tests.
• Extract workspace helpers (getWorkspaceDir, resolveWorkspacePath) and reuse them in lockfile detection.

Reviewed changes

Copilot reviewed 9 out of 10 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/utils.ts	Adds workspace/path helpers and reuses them in lockfile detection.
src/types.ts	Extends Inputs with nodeVersionFile.
src/node-version-file.ts	Implements Node.js version resolution from supported files.
src/node-version-file.test.ts	Adds unit tests for version-file parsing and path resolution.
src/inputs.ts	Reads node-version-file from action inputs.
src/inputs.test.ts	Updates defaults + adds test coverage for the new input.
src/index.ts	Prefers node-version, otherwise resolves Node version via node-version-file.
action.yml	Declares the new node-version-file input.
README.md	Documents node-version-file and adds usage example + inputs table row.

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[Copilot]

The action entrypoint is dist/index.mjs (per action.yml), but the compiled dist output doesn't include the new node-version-file/resolveNodeVersionFile logic (no references found). Please run the build/pack step and commit the updated dist/index.mjs, otherwise users won't actually get this feature when using the action.

[Copilot]

This test mutates process.env by replacing the entire object. Elsewhere in the repo (e.g. utils.test.ts) the convention is vi.stubEnv(...)/vi.unstubAllEnvs(), which avoids leaking env state between tests and prevents issues with Node's env handling. Consider switching to vi.stubEnv('GITHUB_WORKSPACE', '/workspace') and cleaning up with vi.unstubAllEnvs() in afterEach.

Suggested change

	const originalEnv = process.env;
	beforeEach(() => {
	vi.resetAllMocks();
	process.env = { ...originalEnv, GITHUB_WORKSPACE: "/workspace" };
	});
	afterEach(() => {
	process.env = originalEnv;
	});
	beforeEach(() => {
	vi.resetAllMocks();
	vi.stubEnv("GITHUB_WORKSPACE", "/workspace");
	});
	afterEach(() => {
	vi.unstubAllEnvs();
	});