Update dependencies

pkg/file/file.go

@@ -0,0 +1,19 @@
+package file
+
+import (
+	"crypto/sha1"
+	"encoding/hex"
+	"io/ioutil"
+)
+
+// SHA1 returns the SHA1 of a file.
+func SHA1(filename string) string {
+	hasher := sha1.New()
+	s, err := ioutil.ReadFile(filename)
+	if err != nil {
+		return ""
+	}
+
+	hasher.Write(s)
+	return hex.EncodeToString(hasher.Sum(nil))
+}