7a8
> 	"bytes"
10a12
> 	"io"
451a454,530
> }
> 
> // Decide if two files have the same contents or not.
> // chunkSize is the size of the blocks to scan by; pass 0 to get a sensible default.
> // *Follows* symlinks.
> //
> // May return an error if something else goes wrong; in this case, you should ignore the value of 'same'.
> //
> // derived from https://stackoverflow.com/a/30038571
> // under CC-BY-SA-4.0 by several contributors
> func FileCmp(file1, file2 string, chunkSize int) (same bool, err error) {
> 	if chunkSize == 0 {
> 		chunkSize = 4 * 1024
> 	}
> 
> 	// shortcuts: check file metadata
> 	stat1, err := os.Stat(file1)
> 	if err != nil {
> 		return false, err
> 	}
> 
> 	stat2, err := os.Stat(file2)
> 	if err != nil {
> 		return false, err
> 	}
> 
> 	// are inputs are literally the same file?
> 	if os.SameFile(stat1, stat2) {
> 		return true, nil
> 	}
> 
> 	// do inputs at least have the same size?
> 	if stat1.Size() != stat2.Size() {
> 		return false, nil
> 	}
> 
> 	// long way: compare contents
> 	f1, err := os.Open(file1)
> 	if err != nil {
> 		return false, err
> 	}
> 	defer f1.Close()
> 
> 	f2, err := os.Open(file2)
> 	if err != nil {
> 		return false, err
> 	}
> 	defer f2.Close()
> 
> 	b1 := make([]byte, chunkSize)
> 	b2 := make([]byte, chunkSize)
> 	for {
> 		n1, err1 := io.ReadFull(f1, b1)
> 		n2, err2 := io.ReadFull(f2, b2)
> 
> 		// https://pkg.go.dev/io#Reader
> 		// > Callers should always process the n > 0 bytes returned
> 		// > before considering the error err. Doing so correctly
> 		// > handles I/O errors that happen after reading some bytes
> 		// > and also both of the allowed EOF behaviors.
> 
> 		if !bytes.Equal(b1[:n1], b2[:n2]) {
> 			return false, nil
> 		}
> 
> 		if (err1 == io.EOF && err2 == io.EOF) || (err1 == io.ErrUnexpectedEOF && err2 == io.ErrUnexpectedEOF) {
> 			return true, nil
> 		}
> 
> 		// some other error, like a dropped network connection or a bad transfer
> 		if err1 != nil {
> 			return false, err1
> 		}
> 		if err2 != nil {
> 			return false, err2
> 		}
> 	}