fix(cli): use os.homedir() for home directory warning check

[TirthNaik-99]

The home directory warning incorrectly used the core homedir() helper
which respects the GEMINI_CLI_HOME environment variable. When
GEMINI_CLI_HOME is set to a non-home directory, the warning could fire
in subdirectories or miss the actual home directory entirely.

Switch to Node's native os.homedir() so the check always compares
against the real OS home directory, and normalize both resolved paths
before comparison to handle trailing-slash and separator edge cases.

Add test coverage for subdirectories, symlinked home directories, and
GEMINI_CLI_HOME override scenarios.

Fixes #22309

Summary

Fix home directory warning triggering incorrectly in subdirectories by using os.homedir() instead of the core homedir() helper, and normalizing paths before comparison.

Details

• The core homedir() from @google/gemini-cli-core respects the GEMINI_CLI_HOME env var, which is intended for config directory resolution — not for checking if the user is literally in their OS home directory. Replaced with Node's native os.homedir().
• Added path.normalize() on both fs.realpath() outputs before the === comparison to handle trailing-slash and separator edge cases across platforms.
• Added 4 new test cases: subdirectory of home, symlinked home + subdirectory, symlinked home (exact match), and GEMINI_CLI_HOME override scenario.

Related Issues

Fixes #22309

How to Validate

1. Run the unit tests: npx vitest run packages/cli/src/utils/userStartupWarnings.test.ts - All 13 tests should pass.
2. Run the type check: npx tsc --noEmit -p packages/cli/tsconfig.json
3. Run the build: npm run build
4. Manual validation:
   • Run gemini from your home directory (cd ~) — warning should appear
   • Run gemini from a subdirectory (cd ~/some-project) — warning should NOT appear

Pre-Merge Checklist

• Updated relevant documentation and README (if needed)
• Added/updated tests (if needed)
• Noted breaking changes (if any)
• Validated on required platforms/methods:
  • MacOS
    • npm run
    • npx
    • Docker
    • Podman
    • Seatbelt
  • Windows
    • npm run
    • npx
    • Docker
  • Linux
    • npm run
    • npx
    • Docker

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses an issue where the Gemini CLI incorrectly triggers a home directory warning when running in subdirectories. By switching to the native OS home directory resolution and adding path normalization, the CLI now accurately distinguishes between the actual home directory and its subdirectories, improving the user experience and preventing unnecessary warnings.

Highlights

• Home Directory Detection: Replaced the core homedir() helper with Node's native os.homedir() to ensure the warning check correctly identifies the OS home directory regardless of GEMINI_CLI_HOME overrides.
• Path Normalization: Implemented path.normalize() on both workspace and home directory paths to prevent false positives caused by trailing slashes or platform-specific separator differences.
• Test Coverage: Added comprehensive test cases covering subdirectories, symlinked home directories, and environment variable overrides to ensure robust warning behavior.

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[gemini-code-assist]

Code Review

This pull request updates the home directory detection logic in userStartupWarnings.ts by switching to node:os and applying path normalization to handle symlinks and subdirectories correctly. It also adds several test cases to verify these scenarios. One review comment identifies a violation of the repository's testing style guide, specifically recommending the use of vi.stubEnv() instead of direct process.env modification to prevent test leakage.

[gemini-code-assist]

Directly modifying process.env is discouraged in this repository as it can lead to test leakage and is less reliable than using built-in Vitest utilities. Per the repository style guide, you should use vi.stubEnv() to set environment variables. Please also ensure that vi.unstubAllEnvs() is added to the afterEach block (around line 65) to properly clean up the environment after each test.

Suggested change

	await fs.mkdir(projectDir, { recursive: true });
	const originalEnv = process.env['GEMINI_CLI_HOME'];
	process.env['GEMINI_CLI_HOME'] = projectDir;
	const warnings = await getUserStartupWarnings({}, projectDir);
	expect(warnings.find((w) => w.id === 'home-directory')).toBeUndefined();
	if (originalEnv === undefined) {
	delete process.env['GEMINI_CLI_HOME'];
	} else {
	process.env['GEMINI_CLI_HOME'] = originalEnv;
	vi.stubEnv('GEMINI_CLI_HOME', projectDir);
	const warnings = await getUserStartupWarnings({}, projectDir);
	expect(warnings.find((w) => w.id === 'home-directory')).toBeUndefined();

References

1. When testing code that depends on environment variables, use vi.stubEnv('NAME', 'value') in beforeEach and vi.unstubAllEnvs() in afterEach. Avoid modifying process.env directly as it can lead to test leakage and is less reliable. ^(link)