perf: use COPYFILE_FICLONE mode when copying files

[chenjiahan]

Summary

Leverage fs.constants.COPYFILE_FICLONE in fs.cp to take advantage of copy-on-write optimizations

This allows faster file copying when supported by the underlying file system, while gracefully falling back to normal copying on unsupported platforms.

Related Links

• fs: Change the default value of mode argument of fs.copyFile() to fs.constants.COPYFILE_FICLONE nodejs/node#47861
• https://nodejs.org/api/fs.html#fspromisescpsrc-dest-options

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

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[Copilot]

Pull Request Overview

This PR adds the COPYFILE_FICLONE mode flag to file copy operations and ensures the fs.promises.cp call is properly awaited in the server plugin. The change aims to optimize file copying by attempting copy-on-write operations when supported by the filesystem.

• Added await keyword to fs.promises.cp call in server plugin
• Added mode: fs.constants.COPYFILE_FICLONE option to copy operations in both production and test code

Reviewed Changes

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

File	Description
packages/core/src/plugins/server.ts	Added await to fs.promises.cp and COPYFILE_FICLONE mode for publicDir copying
e2e/helper/fixture.ts	Added COPYFILE_FICLONE mode flag to test fixture copy operation

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[Copilot]

The mode parameter with COPYFILE_FICLONE is intended for fs.copyFile(), not fs.promises.cp(). When using fs.promises.cp() with recursive: true for directory copying, the mode parameter controls file permissions, not copy behavior flags. Using COPYFILE_FICLONE here may cause the copy operation to fail on filesystems that don't support copy-on-write, or may not have the intended effect. Consider removing this option or handling filesystem compatibility errors explicitly in the catch block.

Suggested change

mode: fs.constants.COPYFILE_FICLONE,

[Copilot]

The mode parameter with COPYFILE_FICLONE is intended for fs.copyFile(), not fs.promises.cp(). When using fs.promises.cp() with recursive: true for directory copying, the mode parameter controls file permissions, not copy behavior flags. This could cause test failures on filesystems that don't support copy-on-write. Consider removing this option to ensure test stability across different environments.

Suggested change

mode: fsConstants.COPYFILE_FICLONE,