[RSDK-2519] add version information (#83)

Makefile

@@ -1,6 +1,9 @@
 BUILD_CHANNEL?=local
 TOOL_BIN = bin/gotools/$(shell uname -s)-$(shell uname -m)
 PATH_WITH_TOOLS="`pwd`/$(TOOL_BIN):${PATH}"
+GIT_REVISION = $(shell git rev-parse HEAD | tr -d '\n')
+TAG_VERSION?=$(shell git tag --points-at | sort -Vr | head -n1)
+GO_BUILD_LDFLAGS = -ldflags "-X 'main.Version=${TAG_VERSION}' -X 'main.GitRevision=${GIT_REVISION}'"
 
 set-pkg-config-openssl:
 	pkg-config openssl || export PKG_CONFIG_PATH=$$PKG_CONFIG_PATH:`find \`which brew > /dev/null && brew --prefix\` -name openssl.pc | head -n1 | xargs dirname`
@@ -81,7 +84,7 @@ else
 endif
 
 build-module:
-	mkdir -p bin && go build -o bin/cartographer-module module/main.go
+	mkdir -p bin && go build $(GO_BUILD_LDFLAGS) -o bin/cartographer-module module/main.go
 
 install-lua-files:
 	sudo mkdir -p /usr/local/share/cartographer/lua_files/

module/main.go

@@ -3,6 +3,8 @@ package main
 
 import (
 	"context"
+	"fmt"
+	"strings"
 
 	"github.com/edaniels/golog"
 	"go.viam.com/rdk/module"
@@ -12,11 +14,37 @@ import (
 	viamcartographer "github.com/viamrobotics/viam-cartographer"
 )
 
+// Versioning variables which are replaced by LD flags.
+var (
+	Version     = "development"
+	GitRevision = ""
+)
+
 func main() {
 	utils.ContextualMain(mainWithArgs, golog.NewLogger("cartographerModule"))
 }
 
 func mainWithArgs(ctx context.Context, args []string, logger golog.Logger) error {
+	var versionFields []interface{}
+	if len(args) != 2 {
+		return fmt.Errorf("usage: %s [socket path] start module\nor: %s --version        print version & exit", args[0], args[0])
+	}
+	if Version != "" {
+		versionFields = append(versionFields, "version", Version)
+	}
+	if GitRevision != "" {
+		versionFields = append(versionFields, "git_rev", GitRevision)
+	}
+	if len(versionFields) != 0 {
+		logger.Infow(viamcartographer.Model.String(), versionFields...)
+	} else {
+		logger.Info(viamcartographer.Model.String() + " built from source; version unknown")
+	}
+
+	if strings.HasSuffix(args[1], "-version") {
+		return nil
+	}
+
 	// Instantiate the module
 	cartoModule, err := module.NewModuleFromArgs(ctx, logger)
 	if err != nil {