Compile version information into GRV

Author: rgburke

Makefile

@@ -1,10 +1,16 @@
+VERSION=$(shell git describe --long --tags --dirty --always 2>/dev/null || echo 'Unknown')
+HEAD_OID=$(shell git rev-parse --short HEAD 2>/dev/null || echo 'Unknown')
+BUILD_DATETIME=$(shell date '+%Y-%m-%d %H:%M:%S %Z')
+
 GOCMD=go
 GOLINT=golint
 
 BINARY?=grv
 SOURCE_DIR=./cmd/grv
-BUILD_FLAGS=--tags static
-STATIC_BUILD_FLAGS=$(BUILD_FLAGS) -ldflags "-extldflags '-lncurses -ltinfo -lgpm -static'"
+LDFLAGS=-X 'main.version=$(VERSION)' -X 'main.headOid=$(HEAD_OID)' -X 'main.buildDateTime=$(BUILD_DATETIME)'
+STATIC_LDFLAGS=-extldflags '-lncurses -ltinfo -lgpm -static'
+BUILD_FLAGS=--tags static -ldflags "$(LDFLAGS)"
+STATIC_BUILD_FLAGS=--tags static -ldflags "$(LDFLAGS) $(STATIC_LDFLAGS)"
 
 GRV_DIR:=$(dir $(realpath $(lastword $(MAKEFILE_LIST))))
 GOPATH_DIR:=$(GRV_DIR)../../../..

cmd/grv/main.go

@@ -15,14 +15,26 @@ const (
 	MnLogLevelDefault = "NONE"
 )
 
+var (
+	version       = "Unknown"
+	headOid       = "Unknown"
+	buildDateTime = "Unknown"
+)
+
 type grvArgs struct {
 	repoFilePath string
 	logLevel     string
 	logFilePath  string
+	version      bool
 }
 
 func main() {
 	args := parseArgs()
+	if args.version {
+		printVersion()
+		return
+	}
+
 	InitialiseLogging(args.logLevel, args.logFilePath)
 
 	log.Debugf("Creating GRV instance")
@@ -45,12 +57,18 @@ func parseArgs() *grvArgs {
 	repoFilePathPtr := flag.String("repoFilePath", mnRepoFilePathDefault, "Repository file path")
 	logLevelPtr := flag.String("logLevel", MnLogLevelDefault, "Logging level [NONE|PANIC|FATAL|ERROR|WARN|INFO|DEBUG]")
 	logFilePathPtr := flag.String("logFile", mnLogFilePathDefault, "Log file path")
+	versionPtr := flag.Bool("version", false, "Print version")
 
 	flag.Parse()
 
 	return &grvArgs{
 		repoFilePath: *repoFilePathPtr,
 		logLevel:     *logLevelPtr,
 		logFilePath:  *logFilePathPtr,
+		version:      *versionPtr,
 	}
 }
+
+func printVersion() {
+	fmt.Printf("GRV - Git Repository Viewer %v (commit: %v, compiled: %v)\n", version, headOid, buildDateTime)
+}