Add support for an additional exclusion file besides .gitignore and .geminiignore

[alisa-alisa]

Summary

Adding ability to provide an additional exclusion file. It can be provided via a2a-server via an env variable CUSTOM_IGNORE_FILE_PATH.

Details

Support for additional ignore file types are needed to support capabilities such as Gemini Code Assist - Code Customization, which relies on .aiexclude, Users may wish to define their own code customization filename/patterns.

The file is required to take precedence over everything else what seems logical - if a third-party provides an exclusion, they might want to have it prioritized.

Not a breaking change.

Related Issues

Fixes #7439 #4688

How to Validate

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 @alisa-alisa, 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 significantly enhances the file filtering mechanism by introducing support for a custom ignore file. This feature is essential for integrating with external tools, such as Gemini Code Assist, which may require specific exclusion patterns. By allowing a custom ignore file whose rules are prioritized, the system gains greater flexibility and control over which files are processed, without altering existing .gitignore or .geminiignore configurations.

Highlights

• Custom Ignore File Support: Introduced the ability to specify an additional exclusion file via the CUSTOM_IGNORE_FILE_PATH environment variable, allowing for more flexible file filtering.
• Prioritization of Custom Exclusions: The patterns defined in the custom ignore file now take precedence over existing .gitignore and .geminiignore rules, ensuring that third-party exclusions are respected.
• Refactored Ignore File Parsing: The GeminiIgnoreParser has been refactored and renamed to a more generic IgnoreFileParser, making it reusable for different types of ignore files.

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[gemini-code-assist]

Code Review

This pull request adds support for a custom ignore file, which is a great feature. The implementation is mostly correct, but I found a critical issue in the file filtering logic that breaks the precedence rules for ignore patterns. The current implementation can cause files that should be un-ignored by the custom file to be incorrectly filtered out. I've provided a detailed comment with a suggested fix for this issue.

[bdmorgan]

Hi @alisa-alisa, thank you so much for your contribution to Gemini CLI! We really appreciate the time and effort you've put into this.

We're making some updates to our contribution process to improve how we track and review changes. Please take a moment to review our recent discussion post: Improving Our Contribution Process & Introducing New Guidelines.

Key Update: Starting January 26, 2026, the Gemini CLI project will require all pull requests to be associated with an existing issue. Any pull requests not linked to an issue by that date will be automatically closed.

Thank you for your understanding and for being a part of our community!

[adamfweidman]

overall looks good!

A few larger comments:

• Can we support multiple custom ignore file paths? customIgnoreFilePaths would be an optional array of strings (pattern precedence based on ordering in the array).
• Make this a configurable settings rather than just settable via env vars

[adamfweidman]

This will address #4688

[alisa-alisa]

Addressed comments.

[adamfweidman]

/gemini review

[gemini-code-assist]

Code Review

The pull request introduces support for additional exclusion files beyond .gitignore and .geminiignore, configurable via customIgnoreFilePaths in settings and an environment variable. This enhancement centralizes ignore logic within FileDiscoveryService and ensures proper precedence for custom ignore patterns. Documentation and test cases have been updated to reflect these changes, including refactoring the GeminiIgnoreParser into a more generic IgnoreFileParser to handle multiple ignore file types. Review comments address minor test cleanup, a missing property in a test mock, and a potential robustness issue with parsing file paths from an environment variable.

[gemini-code-assist]

Code Review

The pull request successfully introduces support for custom ignore files, enhancing the flexibility of file filtering within the CLI. The refactoring to use a generic IgnoreFileParser and centralizing the ignore logic within FileDiscoveryService is a significant improvement, promoting better maintainability and extensibility. The changes are well-tested and documented.