add version subcommand to both binaries

Signed-off-by: Josh Dolitsky <josh@dolit.ski>

.goreleaser.yml

@@ -7,7 +7,7 @@ builds:
     flags:
       - -trimpath
     ldflags:
-      - "-s -w"
+      - "-s -w -X main.Version={{.Version}}"
     goarch:
       - amd64
       - arm
@@ -29,7 +29,7 @@ builds:
     flags:
       - -trimpath
     ldflags:
-      - "-s -w"
+      - "-s -w -X main.Version={{.Version}}"
     goarch:
       - amd64
       - arm

Makefile

@@ -1,3 +1,12 @@
+SHELL   = /usr/bin/env bash
+GIT_SHA = $(shell git rev-parse --short HEAD)
+GIT_TAG = $(shell git describe --tags --abbrev=0 --exact-match 2>/dev/null)
+
+VERSION = ${GIT_TAG}
+ifeq ($(VERSION),)
+	VERSION = ${GIT_SHA}-devel
+endif
+
 .PHONY: fetch-helpers
 fetch-helpers:
 	for i in $(shell find mappings -name '*.yml' -exec basename {} .yml \;); do \
@@ -14,18 +23,22 @@ vendor:
 
 .PHONY: build-magic
 build-magic:
-	go build -o bin/docker-credential-magic \
+	go build -ldflags="-X main.Version=$(VERSION)" \
+		-o bin/docker-credential-magic \
 		.../cmd/docker-credential-magic
 
 .PHONY: build-magic-embedded
 build-magic-embedded:
 	GOOS=linux GOARCH=amd64 \
-		go build -o pkg/magician/credential-helpers/docker-credential-magic \
+		go build -ldflags="-X main.Version=$(VERSION)" \
+			-o pkg/magician/credential-helpers/docker-credential-magic \
 			.../cmd/docker-credential-magic
 
 .PHONY: build-magician
 build-magician:
-	go build -o bin/docker-credential-magician .../cmd/docker-credential-magician
+	go build -ldflags="-X main.Version=$(VERSION)" \
+		-o bin/docker-credential-magician \
+		.../cmd/docker-credential-magician
 
 .PHONY: test
 test:

cmd/docker-credential-magic/main.go

@@ -21,6 +21,10 @@ const (
 )
 
 var (
+	// Version can be set via:
+	// -ldflags="-X main.Version=$TAG"
+	Version string
+
 	errorInvalidDomain = errors.New("supplied domain is invalid")
 
 	// TODO: should use existing cred helper/docker config if no match
@@ -31,6 +35,19 @@ var (
 )
 
 func main() {
+	args := os.Args
+	if len(args) < 2 {
+		usage()
+	}
+	subcommand := args[1]
+	if subcommand != "get" && subcommand != "version" {
+		usage()
+	}
+	if subcommand == "version" {
+		version()
+	}
+
+	// Assume subcommand is "get" here and read from stdin
 	scanner := bufio.NewScanner(os.Stdin)
 	scanner.Scan()
 	rawInput := scanner.Text()
@@ -61,6 +78,16 @@ func main() {
 	}
 }
 
+func usage() {
+	fmt.Println("Usage: docker-credential-magic <get|version>")
+	os.Exit(1)
+}
+
+func version() {
+	fmt.Println(Version)
+	os.Exit(0)
+}
+
 func parseDomain(s string) (string, error) {
 	parts := strings.Split(s, ".")
 	numParts := len(parts)

cmd/docker-credential-magician/main.go

@@ -1,18 +1,24 @@
 package main
 
 import (
-	"github.com/spf13/cobra"
+	"fmt"
 	"log"
 	"os"
 
+	"github.com/spf13/cobra"
+
 	"github.com/docker-credential-magic/docker-credential-magic/pkg/magician"
 )
 
 type mutateSettings struct {
-	Tag string
+	Tag            string
 	IncludeHelpers []string
 }
 
+// Version can be set via:
+// -ldflags="-X main.Version=$TAG"
+var Version string
+
 func main() {
 	var mutate mutateSettings
 
@@ -21,8 +27,22 @@ func main() {
 		Short: "Augment images with various credential helpers (including magic)",
 	}
 
+	versionCmd := &cobra.Command{
+		Use:   "version",
+		Short: "Print the version and exit",
+		RunE: func(cmd *cobra.Command, args []string) error {
+			if Version == "" {
+				fmt.Println("could not determine build information")
+			} else {
+				fmt.Println(Version)
+			}
+			return nil
+		},
+	}
+	rootCmd.AddCommand(versionCmd)
+
 	mutateCmd := &cobra.Command{
-		Use: "mutate",
+		Use:   "mutate",
 		Short: "Augment an image with one or more credential helpers",
 		Args:  cobra.MinimumNArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {