feat(consistent symlink): modify the IsSymlink method to identify both legacy as well as standard representation

[anushka567]

Description

This PR updates the IsSymlink method in GCSFuse to recognize both the legacy GCSFuse-specific symlink representation and the standard GCS symlink representation used by clients like Storage Transfer Service (STS)

Context: go/sts-consistent-symlink-handling-in-gcsfuse

Link to the issue in case of a bug fix.

b/489240501

Testing details

1. Manual - Yes
2. Unit tests - Added.
3. Integration tests - NA

Any backward incompatible change? If so, please explain.

No

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.32%. Comparing base (d724e63) to head (376c673).
⚠️ Report is 5 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #4428   +/-   ##
=======================================
  Coverage   83.31%   83.32%           
=======================================
  Files         163      163           
  Lines       19997    20000    +3     
=======================================
+ Hits        16661    16665    +4     
+ Misses       2717     2716    -1     
  Partials      619      619           

Flag	Coverage Δ
unittests	83.32% <100.00%> (+<0.01%)	⬆️

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[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 significantly improves GCSFuse's interoperability by enabling it to consistently recognize symlinks created by various Google Cloud clients, including Storage Transfer Service (STS). By updating the symlink detection logic to support both legacy and standard GCS symlink formats, GCSFuse can now provide a more unified and reliable experience for users working with symbolic links across different Google Cloud services.

Highlights

• Enhanced Symlink Recognition: The IsSymlink method has been updated to identify both the legacy GCSFuse-specific symlink representation (gcsfuse_symlink_target) and the standard GCS symlink representation (goog-reserved-file-is-symlink) used by clients like Storage Transfer Service (STS).
• Deprecation Notice: A comment has been added to internal/fs/inode/symlink.go explicitly marking SymlinkMetadataKey as deprecated and retained solely for backward compatibility.
• New Unit Tests: New unit tests were introduced in internal/fs/inode/symlink_test.go to cover the correct recognition of the standard symlink metadata key, ensuring robust handling of both 'true' and 'false' values.

Changelog

• internal/fs/inode/symlink.go
  • Added a deprecation note for the SymlinkMetadataKey constant.
  • Modified the IsSymlink function to check for both the legacy SymlinkMetadataKey and the standard StandardSymlinkMetadataKey.
• internal/fs/inode/symlink_test.go
  • Added TestIsSymLinkWhenStandardMetadataKeyIsPresent to verify IsSymlink with the standard key set to 'true'.
  • Added TestIsSymLinkWhenStandardMetadataKeyIsFalse to verify IsSymlink with the standard key set to 'false'.

Activity

• No human activity has been recorded on this pull request yet.

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[gemini-code-assist]

Code Review

The pull request updates the IsSymlink function to support a new StandardSymlinkMetadataKey for identifying symlinks, while maintaining backward compatibility with the deprecated SymlinkMetadataKey. The updated logic now checks for the legacy key's presence first, and if not found, then checks if the StandardSymlinkMetadataKey has a value of "true". A deprecation note has been added for the legacy key, and new unit tests have been introduced to validate the IsSymlink function's behavior with the new standard metadata key.