feat: use git tags for versioning via ldflags instead of hardcoded version

Replace the hardcoded version string with build-time injection using
-ldflags. Version, build time, and git commit are now derived from git
tags and injected by both the Makefile and GoReleaser.

Author: tito

.goreleaser.yaml

@@ -32,7 +32,10 @@ builds:
       # - windows_arm64
       # - android_arm64
     ldflags:
-      - "-s -w -X 'main.version={{ .Tag }}'"
+      - -s -w
+      - -X main.version={{.Version}}
+      - -X main.buildTime={{.Date}}
+      - -X main.gitCommit={{.Commit}}
 
 upx:
   - enabled: true

Makefile

@@ -1,7 +1,10 @@
 NAME=greyproxy
 BINDIR=bin
-VERSION=$(shell cat cmd/greyproxy/version.go | grep 'version =' | sed 's/.*\"\(.*\)\".*/\1/g')
-GOBUILD=CGO_ENABLED=0 go build --ldflags="-s -w" -v -x -a
+VERSION=$(shell git describe --tags --always --dirty 2>/dev/null || echo "dev")
+BUILD_TIME=$(shell date -u '+%Y-%m-%dT%H:%M:%SZ')
+GIT_COMMIT=$(shell git rev-parse HEAD 2>/dev/null || echo "unknown")
+LDFLAGS=-s -w -X main.version=$(VERSION) -X main.buildTime=$(BUILD_TIME) -X main.gitCommit=$(GIT_COMMIT)
+GOBUILD=CGO_ENABLED=0 go build --ldflags="$(LDFLAGS)" -v -x -a
 GOFILES=cmd/greyproxy/*.go
 
 PLATFORM_LIST = \

cmd/greyproxy/main.go

@@ -95,8 +95,8 @@ func parseFlags() {
 	flag.Parse()
 
 	if printVersion {
-		fmt.Fprintf(os.Stdout, "greyproxy %s (%s %s/%s)\n",
-			version, runtime.Version(), runtime.GOOS, runtime.GOARCH)
+		fmt.Fprintf(os.Stdout, "greyproxy %s (%s %s/%s)\n  built:  %s\n  commit: %s\n",
+			version, runtime.Version(), runtime.GOOS, runtime.GOARCH, buildTime, gitCommit)
 		os.Exit(0)
 	}
 }
@@ -143,8 +143,8 @@ func main() {
 		handleUninstall(os.Args[2:])
 
 	case "-V", "--version":
-		fmt.Fprintf(os.Stdout, "greyproxy %s (%s %s/%s)\n",
-			version, runtime.Version(), runtime.GOOS, runtime.GOARCH)
+		fmt.Fprintf(os.Stdout, "greyproxy %s (%s %s/%s)\n  built:  %s\n  commit: %s\n",
+			version, runtime.Version(), runtime.GOOS, runtime.GOARCH, buildTime, gitCommit)
 
 	default:
 		printUsage()

cmd/greyproxy/version.go

@@ -1,5 +1,8 @@
 package main
 
+// Build-time variables (set via -ldflags)
 var (
-	version = "0.2.0"
+	version   = "dev"
+	buildTime = "unknown"
+	gitCommit = "unknown"
 )