Inject git version when building a release

Makefile

@@ -1,3 +1,5 @@
+TARGETS = darwin/amd64 darwin/386 linux/amd64 linux/386 windows/amd64 windows/386
+GIT_COMMIT = $(shell git rev-parse HEAD)
 DOCKER_RELEASE_TAG = "sosedoff/pgweb:$(shell git describe --abbrev=0 --tags | sed 's/v//')"
 BINDATA_IGNORE = $(shell git ls-files -io --exclude-standard $< | sed 's/^/-ignore=/;s/[.]/[.]/g')
 
@@ -37,7 +39,10 @@ build: assets
 	@echo "You can now execute ./pgweb"
 
 release: assets
-	gox -osarch="darwin/amd64 darwin/386 linux/amd64 linux/386 windows/amd64 windows/386" -output="./bin/pgweb_{{.OS}}_{{.Arch}}"
+	gox \
+		-osarch="$(TARGETS)" \
+		-ldflags "-X main.GitCommit $(GIT_COMMIT)" \
+		-output="./bin/pgweb_{{.OS}}_{{.Arch}}"
 
 bootstrap:
 	gox -build-toolchain

main.go

@@ -16,6 +16,9 @@ import (
 
 const VERSION = "0.5.2"
 
+// The git commit that was compiled. This will be filled in by the compiler.
+var GitCommit string
+
 var options command.Options
 
 func exitWithMessage(message string) {
@@ -61,11 +64,20 @@ func initOptions() {
 	options = command.Opts
 
 	if options.Version {
-		fmt.Printf("pgweb v%s\n", VERSION)
+		printVersion()
 		os.Exit(0)
 	}
 
-	fmt.Println("Pgweb version", VERSION)
+	printVersion()
+}
+
+func printVersion() {
+	str := fmt.Sprintf("Pgweb v%s", VERSION)
+	if GitCommit != "" {
+		str += fmt.Sprintf(" (git: %s)", GitCommit)
+	}
+
+	fmt.Println(str)
 }
 
 func startServer() {