cowsync

cowsync is a local filesystem sync tool similar to rsync, but focused on fast copy-on-write cloning when the platform supports it.

It is intended for local tree-to-tree sync where cheap CoW clones are preferred and a regular byte-for-byte copy is an acceptable fallback.

Status

Current behavior:

• walks a source tree
• filters files with --include and --exclude
• creates destination directories as needed
• clones files with copy-on-write when available
• falls back to normal file copy when cloning is unsupported

Current non-features:

• no deletion of extra destination files
• no remote sync
• no checksums
• no unchanged-file skipping yet

Platforms

• macOS: uses clonefile
• Linux: uses FICLONE
• other platforms: falls back to std::fs::copy

Build

cargo build

Install

From crates.io after publish:

cargo install cowsync

From a local checkout:

cargo install --path .

Usage

cowsync <src> <dst> [--include <glob>]... [--exclude <glob>]... [--dry-run] [--verbose]

Examples:

cowsync src dst
cowsync src dst --include 'src/**' --exclude '*.log'
cowsync src dst --include node_modules
cowsync src dst --dry-run --verbose

Filter Semantics

• If no --include rules are provided, all files are included by default.
• --exclude rules take precedence over --include.
• Matching is evaluated relative to the source root.
• Bare directory patterns like node_modules match the whole subtree under that directory.

Dry Run And Verbose

• --dry-run prints planned operations only when combined with --verbose.
• --verbose prints each file operation as clone <src> -> <dst>.

Notes

• Existing destination files at matched paths are overwritten.
• Extra files already present in the destination are left untouched.