From eced7be07c6ef6d5d983feb11b595c1603ffc9fb Mon Sep 17 00:00:00 2001
From: Steve Milner <smilner@redhat.com>
Date: Fri, 13 Oct 2017 15:50:00 -0400
Subject: [PATCH] dockertar-sha256-helper: Error without arg

Provide a human understandable error when an argument is not provided.

Signed-off-by: Steve Milner <smilner@redhat.com>

Closes: #1117
Approved by: giuseppe
---
 dockertar-sha256-helper.go | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/dockertar-sha256-helper.go b/dockertar-sha256-helper.go
index 4a4498ff..3e0793e9 100644
--- a/dockertar-sha256-helper.go
+++ b/dockertar-sha256-helper.go
@@ -1,14 +1,18 @@
 package main
 
 import (
-	"fmt"
 	"compress/gzip"
-	"os"
-	"io"
 	"crypto/sha256"
+	"fmt"
+	"io"
+	"os"
 )
 
 func main() {
+	// Require one positional argument
+	if len(os.Args) != 2 {
+		panic("One positional argument is required")
+	}
 	reader, err := os.Open(os.Args[1])
 	if err != nil {
 		os.Exit(1)