# CopySure (CLI prototype)

Checksum-verified file copy with resumable jobs and a diff mode. Working
prototype of the CopySure concept's core engine — see `../plan.md` for the
full product plan (Explorer integration and sync rules are still on the
roadmap; this build is the copy/verify/diff engine only).

## Build from source

Requires Go 1.24+, no external dependencies.

```
go build -o copysure .
```

Cross-compile for another platform:

```
GOOS=windows GOARCH=amd64 go build -o copysure.exe .
GOOS=darwin  GOARCH=arm64 go build -o copysure .
```

## Usage

```
copysure copy <src> <dst> [--workers N]
copysure diff <src> <dst>
```

`copy` walks `<src>`, and for every file: if the destination already has a
file with the same SHA-256 hash, it's skipped (safe to re-run / resume a
partial job); otherwise the file is copied and immediately re-read from
disk and re-hashed against the source before being counted as done. A
hash mismatch after copy is reported, not silently accepted.

`diff` compares two trees by content hash without copying anything —
useful to verify a copy job that ran elsewhere, or to preview what a
`copy` run would actually change.

## Prebuilt binaries

See `../downloads/` for prebuilt binaries (Windows/macOS/Linux, amd64 +
darwin/arm64) and `CHECKSUMS.txt` for their SHA-256 hashes. These are
unsigned indie builds — Windows SmartScreen and macOS Gatekeeper will warn
on first run, which is expected until a code-signing certificate is in
place (see the build plan's risk section).