fix: report the installed version for go install builds

main.go

@@ -29,14 +29,37 @@ import (
 	"io"
 	"os"
 	"os/exec"
+	"runtime/debug"
 	"strconv"
 	"strings"
 
 	"github.com/DivergentCodes/commitlint/lint"
 )
 
+// version is stamped by the release workflow via -ldflags. Builds that are not
+// produced by that workflow — notably `go install ...@v1.2.3`, the documented
+// install path — leave it at the default, so fall back to the version the Go
+// toolchain recorded in the binary.
 var version = "0.0.0-dev"
 
+// resolveVersion prefers an ldflags-stamped version, then the module version
+// embedded by `go install`, and otherwise reports the default.
+func resolveVersion() string {
+	if version != "0.0.0-dev" {
+		return version
+	}
+	info, ok := debug.ReadBuildInfo()
+	if !ok || info.Main.Version == "" {
+		return version
+	}
+	// A build from a local directory records "(devel)", which is less
+	// informative than the default.
+	if info.Main.Version == "(devel)" {
+		return version
+	}
+	return info.Main.Version
+}
+
 func main() {
 	if len(os.Args) < 2 {
 		usage()
@@ -46,7 +69,7 @@ func main() {
 	case "lint":
 		os.Exit(runLint(os.Args[2:]))
 	case "version", "--version", "-v":
-		fmt.Println(version)
+		fmt.Println(resolveVersion())
 	case "help", "--help", "-h":
 		usage()
 	default:

main_test.go

@@ -144,3 +144,24 @@ func TestWriteTextSkipsPassingMessages(t *testing.T) {
 		t.Errorf("failing message should be printed:\n%s", buf.String())
 	}
 }
+
+// `go install ...@vX.Y.Z` does not run the release workflow's -ldflags, so
+// without a build-info fallback every installed binary reported 0.0.0-dev.
+// Under `go test` the module version is "(devel)", so this cannot assert the
+// installed-version path directly; it pins the precedence and the guarantee
+// that the fallback never surfaces "(devel)" or an empty string.
+func TestResolveVersion(t *testing.T) {
+	orig := version
+	defer func() { version = orig }()
+
+	version = "v2.3.4"
+	if got := resolveVersion(); got != "v2.3.4" {
+		t.Errorf("stamped version should win: got %q, want v2.3.4", got)
+	}
+
+	version = "0.0.0-dev"
+	got := resolveVersion()
+	if got == "" || got == "(devel)" {
+		t.Errorf("fallback must be informative, got %q", got)
+	}
+}