Resolving #21 issue. Adding ko version and simple release script

README.md

@@ -254,6 +254,9 @@ This flag is still experimental, and feedback is very welcome.
 `ko delete` simply passes through to `kubectl delete`. It is exposed purely out
 of convenience for cleaning up resources created through `ko apply`.
 
+### `ko version`
+
+`ko version` prints version of ko. For not released binaries it will print hash of latest commit in current git tree.
 
 ## With `minikube`
 

hack/release.sh

@@ -0,0 +1,30 @@
+#!/usr/bin/env bash
+
+# Copyright 2019 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.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Usage:
+#   hack/release.sh $VERSION
+#
+# Example:
+#   hack/release.sh v0.2
+
+VERSION=$1
+
+KO_ROOT="$(cd "$(dirname "$0")" && pwd)/.."
+
+go get github.com/ahmetb/govvv
+govvv build -o $KO_ROOT/build/ko $KO_ROOT/cmd/ko -pkg github.com/google/ko/pkg/commands -version $VERSION
+git tag $VERSION
+git push origin $VERSION

pkg/commands/commands.go

@@ -23,6 +23,7 @@ import (
 //    https://github.com/google/go-containerregistry/issues/80
 func AddKubeCommands(topLevel *cobra.Command) {
 	addDelete(topLevel)
+	addVersion(topLevel)
 	addCreate(topLevel)
 	addApply(topLevel)
 	addResolve(topLevel)

pkg/commands/version.go

@@ -0,0 +1,51 @@
+// Copyright 2019 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.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package commands
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"os/exec"
+	"strings"
+
+	"github.com/spf13/cobra"
+)
+
+// provided by govvv in compile-time
+var Version string
+
+// addVersion augments our CLI surface with version.
+func addVersion(topLevel *cobra.Command) {
+	topLevel.AddCommand(&cobra.Command{
+		Use:   "version",
+		Short: `Print ko version.`,
+		Run: func(cmd *cobra.Command, args []string) {
+			version()
+		},
+	})
+}
+
+func version() {
+	if Version == "" {
+		gitDir := fmt.Sprintf("--git-dir=%v/src/github.com/google/ko/.git", os.Getenv("GOPATH"))
+		hash, err := exec.Command("git", gitDir, "rev-parse", "HEAD").Output()
+		if err != nil {
+			log.Fatalf("error during command execution: %v", err)
+		}
+		Version = strings.TrimSpace(string(hash))
+	}
+	fmt.Printf("version: %v\n", Version)
+}