Add build version reporting

internal/buildinfo/buildinfo.go

@@ -0,0 +1,36 @@
+// Package buildinfo resolves the product version embedded in a Notarius build.
+package buildinfo
+
+import (
+	"fmt"
+	"regexp"
+	"runtime/debug"
+)
+
+var stableVersion = regexp.MustCompile(`^v(0|[1-9][0-9]*)\.(0|[1-9][0-9]*)\.(0|[1-9][0-9]*)$`)
+
+// Override is set at link time for controlled builds.
+var Override string
+
+// Version returns the release version embedded in the build, or development
+// when the build does not carry a stable release tag.
+func Version() (string, error) {
+	buildVersion := ""
+	if info, ok := debug.ReadBuildInfo(); ok {
+		buildVersion = info.Main.Version
+	}
+	return resolve(Override, buildVersion)
+}
+
+func resolve(override, buildVersion string) (string, error) {
+	if override != "" {
+		if !stableVersion.MatchString(override) {
+			return "", fmt.Errorf("build version override is not a stable release tag")
+		}
+		return override, nil
+	}
+	if stableVersion.MatchString(buildVersion) {
+		return buildVersion, nil
+	}
+	return "development", nil
+}

internal/buildinfo/buildinfo_test.go

@@ -0,0 +1,45 @@
+package buildinfo
+
+import "testing"
+
+func TestResolve(t *testing.T) {
+	tests := []struct {
+		name         string
+		override     string
+		buildVersion string
+		want         string
+		wantErr      bool
+	}{
+		{name: "stable main module version", buildVersion: "v1.2.3", want: "v1.2.3"},
+		{name: "zero version", buildVersion: "v0.0.0", want: "v0.0.0"},
+		{name: "override takes precedence", override: "v2.3.4", buildVersion: "v1.2.3", want: "v2.3.4"},
+		{name: "invalid override", override: "version", buildVersion: "v1.2.3", wantErr: true},
+		{name: "override with whitespace", override: " v1.2.3", wantErr: true},
+		{name: "leading zero major", buildVersion: "v01.2.3", want: "development"},
+		{name: "leading zero minor", buildVersion: "v1.02.3", want: "development"},
+		{name: "leading zero patch", buildVersion: "v1.2.03", want: "development"},
+		{name: "build version with whitespace", buildVersion: "v1.2.3 ", want: "development"},
+		{name: "prerelease", buildVersion: "v1.2.3-rc.1", want: "development"},
+		{name: "build suffix", buildVersion: "v1.2.3+build.1", want: "development"},
+		{name: "pseudo version", buildVersion: "v0.0.0-20260102030405-abcdef123456", want: "development"},
+		{name: "development build", buildVersion: "(devel)", want: "development"},
+		{name: "missing build information", want: "development"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := resolve(tt.override, tt.buildVersion)
+			if tt.wantErr {
+				if err == nil {
+					t.Fatal("resolve() error = nil, want error")
+				}
+				return
+			}
+			if err != nil {
+				t.Fatalf("resolve() error = %v", err)
+			}
+			if got != tt.want {
+				t.Fatalf("resolve() = %q, want %q", got, tt.want)
+			}
+		})
+	}
+}