refactor: replace hand-rolled MIME lookup with mime_guess2

[malob]

Description

Replace the manual mime_from_extension match table (~25 extensions) in executor.rs with the mime_guess2 crate, which provides comprehensive MIME type detection from the Apache MIME database.

Why

Just as I don't think this package should hand-roll RFC 5322 email construction when battle-tested libraries exist (#491), I don't think it should maintain a partial extension-to-MIME mapping when a well-maintained crate covers the full spectrum. The current match table handles common types but file types like .webp, .mp4, .heic, .wasm, .tar.gz, and hundreds of others fall through to the metadata fallback or application/octet-stream.

mime_guess2 is an actively maintained fork of mime_guess (6.5M downloads, MIT licensed, 24KB). It uses a static lookup table from the Apache MIME database — no filesystem access or magic-byte sniffing.

This also lays the foundation for upcoming Gmail attachment support (--attach flag, #247), which will need MIME detection for email attachments via the same crate.

What changed

• Added mime_guess2 = "2.3" to Cargo.toml
• Replaced mime_from_extension() body with mime_guess2::from_path().first()
• Deleted the hand-rolled match table
• All 6 existing test_resolve_upload_mime_* tests pass unchanged

Checklist:

• My code follows the AGENTS.md guidelines (no generated google-* crates).
• I have run cargo fmt --all to format the code perfectly.
• I have run cargo clippy -- -D warnings and resolved all warnings.
• I have added tests that prove my fix is effective or that my feature works.
• I have provided a Changeset file (e.g. via pnpx changeset) to document my changes.

[changeset-bot]

🦋 Changeset detected

Latest commit: 55da988

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@googleworkspace/cli	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[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 refactors the MIME type detection logic by adopting the mime_guess2 crate. This enhancement moves away from a limited, manually maintained mapping to a comprehensive, battle-tested library, ensuring more accurate content-type inference for file uploads. The change improves the reliability of file handling and sets the stage for future functionalities requiring broad MIME type support.

Highlights

• Replaced custom MIME type detection: The hand-rolled mime_from_extension function in src/executor.rs has been replaced with the mime_guess2 crate for more robust and comprehensive MIME type inference.
• Improved MIME type coverage: This change significantly expands the range of detected MIME types beyond the previous ~25 extensions, supporting types like .webp, .mp4, and .wasm, which previously defaulted to application/octet-stream.
• Foundation for future features: Integrating mime_guess2 prepares the codebase for upcoming features such as Gmail attachment support, which will rely on accurate MIME detection.

Changelog

• .changeset/mime-guess-upload.md
  • Added a new changeset file documenting the replacement of the hand-rolled MIME type lookup with mime_guess2.
• Cargo.toml
  • Added mime_guess2 as a new dependency with version 2.3.
• src/executor.rs
  • Replaced the call to the custom mime_from_extension function with mime_guess2::from_path().first().
  • Removed the mime_from_extension helper function and its associated match table.

Activity

• No human activity (comments, reviews) has been recorded on this pull request yet.

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[gemini-code-assist]

Code Review

This pull request is a solid refactoring that replaces a limited, hand-rolled MIME type lookup with the mime_guess2 crate. This change improves maintainability and correctness by leveraging a comprehensive, well-maintained library. The implementation is clean, correct, and properly integrated into the existing logic. I have no high or critical severity issues to report.

[googleworkspace-bot]

/gemini review

[gemini-code-assist]

Code Review

This pull request refactors the MIME type detection by replacing a hand-rolled lookup table with the mime_guess2 crate. This is a good change that improves maintainability and extends functionality to support a much wider range of file types for uploads. The implementation correctly integrates the new crate while preserving the existing fallback logic. After a thorough review, I found no issues with the proposed changes.