refactor(pm): simplify Linux cloner with sync hardlink strategy

[elrrrrrrr]

• The previous implementation tried FICLONE ioctl, then copy_file_range,
  then regular copy - each with separate spawn_blocking calls.

• This simplification uses hardlinks (which are fast and share disk space)
  with copy fallback, all in a single blocking task.

[gemini-code-assist]

Summary of Changes

Hello @elrrrrrrr, 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 file cloning utility, specifically for Linux, to simplify its implementation and improve efficiency. The previous complex multi-stage asynchronous copying mechanism has been replaced with a more straightforward synchronous approach that leverages hardlinks for performance and disk space efficiency, falling back to a direct copy when necessary. This change consolidates blocking I/O operations into a single task, reducing overhead and making the cloning process more robust. Minor structural improvements were also applied to the Windows cloner for consistency.

Highlights

• Linux Cloner Simplification: The Linux file cloning logic has been significantly simplified by removing complex asynchronous fallback mechanisms (FICLONE, copy_file_range) and adopting a synchronous hardlink-first strategy with a regular copy fallback.
• Synchronous Hardlink Strategy: The new Linux implementation prioritizes creating hardlinks for files to save disk space and improve performance. If hardlinking fails, it falls back to a standard file copy.
• Consolidated Blocking Operations: Instead of multiple spawn_blocking calls for different copy methods, the entire directory cloning process on Linux is now handled within one blocking task, streamlining execution.
• Windows Cloner Refinement: The Windows cloner also received minor refactoring, separating the initial directory creation from the recursive copying logic for both fast_copy and clone_dir functions, improving code structure.

Changelog

• crates/pm/src/util/cloner.rs
  • Removed FICLONE and copy_file_range specific logic and related feature flags.
  • Introduced synchronous helper functions (has_install_script_sync, copy_file_sync, clone_dir_sync).
  • Refactored the main linux_clone::clone_dir to use a single spawn_blocking call for the entire cloning process.
  • Updated windows_clone::fast_copy and windows_clone::clone_dir to use internal recursive helper functions (fast_copy_inner, clone_dir_inner) for better structure.

Activity

• No specific activity has been recorded for this pull request yet.

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[gemini-code-assist]

Code Review

This pull request significantly simplifies the file cloning logic for Linux by replacing a complex, multi-stage async implementation with a much cleaner synchronous approach using hardlinks and a copy fallback, all executed within a tokio::task::spawn_blocking call. This is a great improvement for readability and maintainability. The related refactoring in the Windows implementation also improves the code structure. My feedback focuses on enhancing error handling to make the cloning process more robust and improving the formatting of error messages for better diagnostics.