Major revamp.

nixos/overlays/tarsum.go

@@ -0,0 +1,24 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+	"github.com/docker/docker/pkg/tarsum"
+)
+
+func main() {
+	ts, err := tarsum.NewTarSum(os.Stdin, true, tarsum.Version1)
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+
+	if _, err = io.Copy(ioutil.Discard, ts); err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+
+	fmt.Println(ts.Sum(nil))
+}