From 4e88d0c9075e8f8169fa7dae8df938d9c3347bb5 Mon Sep 17 00:00:00 2001
From: "W. Trevor King" <wking@tremily.us>
Date: Fri, 22 Sep 2017 14:48:42 -0700
Subject: [PATCH] tools/cmd/resolve: Keep iterating through ref-engines on
 empty Get

If the ref-engine we're checking returns no results, keep going (even
if it didn't return an error).  Also document the "ref-engine knows it
doesn't have that name" results in the Engine.Get interface.
---
 tools/cmd/resolve.go         | 3 +++
 tools/refengine/interface.go | 2 ++
 2 files changed, 5 insertions(+)

diff --git a/tools/cmd/resolve.go b/tools/cmd/resolve.go
index cc57e0b..8cc2f0a 100644
--- a/tools/cmd/resolve.go
+++ b/tools/cmd/resolve.go
@@ -83,6 +83,9 @@ func resolveCallback(ctx context.Context, allRoots map[string][]refengine.Merkle
 		logrus.Warn(err)
 		return nil
 	}
+	if len(roots) == 0 {
+		return nil
+	}
 	allRoots[name] = roots
 	return resolved
 }
diff --git a/tools/refengine/interface.go b/tools/refengine/interface.go
index e61de51..767d99d 100644
--- a/tools/refengine/interface.go
+++ b/tools/refengine/interface.go
@@ -24,6 +24,8 @@ import (
 type Engine interface {
 
 	// Get returns an array of potential Merkle roots from the store.
+	// When no results are found, roots will be an empty array and err
+	// will be nil.
 	Get(ctx context.Context, name string) (roots []MerkleRoot, err error)
 
 	// Close releases resources held by the engine.  Subsequent engine