From c1e9a85008b2a2d56ca0eb477a5ad4fa04ebe455 Mon Sep 17 00:00:00 2001
From: Simone Gotti <simone.gotti@gmail.com>
Date: Thu, 30 Apr 2015 11:53:13 +0200
Subject: [PATCH] store: define specific error for key not found.

It's needed when you want to know if the key exists.
---
 store/store.go | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/store/store.go b/store/store.go
index 8a9c257..a4f54dc 100644
--- a/store/store.go
+++ b/store/store.go
@@ -20,6 +20,7 @@ import (
 	"crypto/sha512"
 	"database/sql"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"hash"
 	"io"
@@ -59,6 +60,10 @@ var diskvStores = [...]string{
 	"imageManifest",
 }
 
+var (
+	ErrKeyNotFound = errors.New("no keys found")
+)
+
 // Store encapsulates a content-addressable-storage for storing ACIs on disk.
 type Store struct {
 	base      string
@@ -220,7 +225,7 @@ func (s Store) ResolveKey(key string) (string, error) {
 
 	keyCount := len(aciInfos)
 	if keyCount == 0 {
-		return "", fmt.Errorf("no keys found")
+		return "", ErrKeyNotFound
 	}
 	if keyCount != 1 {
 		return "", fmt.Errorf("ambiguous key: %q", key)