Add versioning to dockron binary

.drone.yml

@@ -34,7 +34,7 @@ steps:
     image: golang:1.11
     commands:
       - go get -u github.com/golang/dep/cmd/dep
-      - make build-all-static
+      - make build-linux-static
 
   - name: push image - arm
     image: plugins/docker

.gitignore

@@ -26,6 +26,6 @@ _testmain.go
 
 # Output
 dockron
-dockron-linux-*
+dockron-*
 # deps
 vendor/

Makefile

@@ -1,4 +1,7 @@
 DOCKER_TAG ?= dockron-dev-${USER}
+GIT_TAG_NAME := $(shell git tag -l --contains HEAD)
+GIT_SHA := $(shell git rev-parse HEAD)
+VERSION := $(if $(GIT_TAG_NAME),$(GIT_TAG_NAME),$(GIT_SHA))
 
 .PHONY: default
 default: build
@@ -14,23 +17,38 @@ run: vendor
 
 # Output target
 dockron: vendor
-	go build -o dockron
+	@echo Version: $(VERSION)
+	go build -ldflags '-X "main.version=${VERSION}"' -o dockron
 
 # Alias for building
 .PHONY: build
 build: dockron
 
+dockron-darwin-amd64: vendor
+	GOOS=darwin GOARCH=amd64 CGO_ENABLED=0 \
+		   go build -ldflags '-X "main.version=${VERSION}"' -a -installsuffix nocgo \
+		   -o dockron-darwin-amd64
+
 dockron-linux-amd64: vendor
-	GOARCH=amd64 CGO_ENABLED=0 GOOS=linux go build -a -installsuffix nocgo -o dockron-linux-amd64
+	GOOS=linux GOARCH=amd64 CGO_ENABLED=0 \
+		   go build -ldflags '-X "main.version=${VERSION}"' -a -installsuffix nocgo \
+		   -o dockron-linux-amd64
 
 dockron-linux-arm: vendor
-	GOARCH=arm CGO_ENABLED=0 GOOS=linux go build -a -installsuffix nocgo -o dockron-linux-arm
+	GOOS=linux GOARCH=arm CGO_ENABLED=0 \
+		   go build -ldflags '-X "main.version=${VERSION}"' -a -installsuffix nocgo \
+		   -o dockron-linux-arm
 
 dockron-linux-arm64: vendor
-	GOARCH=arm64 CGO_ENABLED=0 GOOS=linux go build -a -installsuffix nocgo -o dockron-linux-arm64
+	GOOS=linux GOARCH=arm64 CGO_ENABLED=0 \
+		   go build -ldflags '-X "main.version=${VERSION}"' -a -installsuffix nocgo \
+		   -o dockron-linux-arm64
+
+.PHONY: build-linux-static
+build-linux-static: dockron-linux-amd64 dockron-linux-arm dockron-linux-arm64
 
 .PHONY: build-all-static
-build-all-static: dockron-linux-amd64 dockron-linux-arm dockron-linux-arm64
+build-all-static: dockron-darwin-amd64 build-linux-static
 
 # Cleans all build artifacts
 .PHONY: clean

main.go

@@ -7,15 +7,21 @@ import (
 	"github.com/docker/docker/client"
 	"github.com/robfig/cron"
 	"golang.org/x/net/context"
+	"os"
 	"strings"
 	"time"
 )
 
-// WatchInterval is the duration we should sleep until polling Docker
-var DefaultWatchInterval = (1 * time.Minute)
+var (
+	// defaultWatchInterval is the duration we should sleep until polling Docker
+	defaultWatchInterval = (1 * time.Minute)
 
-// SchedLabel is the string label to search for cron expressions
-var SchedLabel = "dockron.schedule"
+	// schedLabel is the string label to search for cron expressions
+	schedLabel = "dockron.schedule"
+
+	// version of dockron being run
+	version = "dev"
+)
 
 // ContainerStartJob represents a scheduled container task
 // It contains a reference to a client, the schedule to run on, and the
@@ -48,7 +54,7 @@ func QueryScheduledJobs(cli *client.Client) (jobs []ContainerStartJob) {
 	}
 
 	for _, container := range containers {
-		if val, ok := container.Labels[SchedLabel]; ok {
+		if val, ok := container.Labels[schedLabel]; ok {
 			jobName := strings.Join(container.Names, "/")
 			jobs = append(jobs, ContainerStartJob{
 				Schedule:    val,
@@ -81,9 +87,16 @@ func main() {
 
 	// Read interval for polling Docker
 	var watchInterval time.Duration
-	flag.DurationVar(&watchInterval, "watch", DefaultWatchInterval, "Interval used to poll Docker for changes")
+	flag.DurationVar(&watchInterval, "watch", defaultWatchInterval, "Interval used to poll Docker for changes")
+	var showVersion = flag.Bool("version", false, "Display the version of dockron and exit")
 	flag.Parse()
 
+	// Print version if asked
+	if *showVersion {
+		fmt.Println("Dockron version:", version)
+		os.Exit(0)
+	}
+
 	// Create a Cron
 	c := cron.New()