Add flag and PublishOption for destination repo

README.md

@@ -68,6 +68,9 @@ e.g.:
 - `KO_DOCKER_REPO=gcr.io/my-project`, or
 - `KO_DOCKER_REPO=my-dockerhub-user`
 
+If both the flag and the environment variable are set, the flag value takes
+precedence.
+
 # Build an Image
 
 `ko publish ./cmd/app` builds and pushes a container image, and prints the

pkg/commands/options/publish.go

@@ -1,4 +1,4 @@
-// Copyright 2018 Google LLC All Rights Reserved.
+// Copyright 2021 Google LLC All Rights Reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -17,6 +17,7 @@ package options
 import (
 	"crypto/md5" //nolint: gosec // No strong cryptography needed.
 	"encoding/hex"
+	"os"
 	"path"
 
 	"github.com/google/ko/pkg/publish"
@@ -25,6 +26,9 @@ import (
 
 // PublishOptions encapsulates options when publishing.
 type PublishOptions struct {
+	// DockerRepo configures the destination image repository
+	DockerRepo string
+
 	Tags []string
 
 	// Push publishes images to a registry.
@@ -46,6 +50,12 @@ type PublishOptions struct {
 }
 
 func AddPublishArg(cmd *cobra.Command, po *PublishOptions) {
+	// Set DockerRepo from the KO_DOCKER_REPO envionment variable.
+	// See https://github.com/google/ko/pull/351 for flag discussion.
+	if dockerRepo, exists := os.LookupEnv("KO_DOCKER_REPO"); exists {
+		po.DockerRepo = dockerRepo
+	}
+
 	cmd.Flags().StringSliceVarP(&po.Tags, "tags", "t", []string{"latest"},
 		"Which tags to use for the produced image instead of the default 'latest' tag "+
 			"(may not work properly with --base-import-paths or --bare).")

pkg/commands/resolver.go

@@ -1,4 +1,4 @@
-// Copyright 2018 Google LLC All Rights Reserved.
+// Copyright 2021 Google LLC All Rights Reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -131,7 +131,7 @@ func makePublisher(po *options.PublishOptions) (publish.Interface, error) {
 	// Create the publish.Interface that we will use to publish image references
 	// to either a docker daemon or a container image registry.
 	innerPublisher, err := func() (publish.Interface, error) {
-		repoName := os.Getenv("KO_DOCKER_REPO")
+		repoName := po.DockerRepo
 		namer := options.MakeNamer(po)
 		if repoName == publish.LocalDomain || po.Local {
 			// TODO(jonjohnsonjr): I'm assuming that nobody will