gt version: Match bd version output format

Single-line output showing version, build type, branch and commit:
  gt version 0.1.0 (dev: main@62413d55cbb0)

Uses runtime/debug to get VCS info from build, with fallback to
git commands at runtime.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/cmd/version.go

@@ -2,16 +2,21 @@ package cmd
 
 import (
 	"fmt"
+	"os/exec"
+	"runtime/debug"
+	"strings"
 
 	"github.com/spf13/cobra"
-	"github.com/steveyegge/gastown/internal/style"
 )
 
 // Version information - set at build time via ldflags
 var (
-	Version   = "0.1.0"
-	BuildTime = "unknown"
-	GitCommit = "unknown"
+	Version = "0.1.0"
+	// Build can be set via ldflags at compile time
+	Build = "dev"
+	// Commit and Branch - the git revision the binary was built from (optional ldflag)
+	Commit = ""
+	Branch = ""
 )
 
 var versionCmd = &cobra.Command{
@@ -19,13 +24,68 @@ var versionCmd = &cobra.Command{
 	GroupID: GroupDiag,
 	Short:   "Print version information",
 	Run: func(cmd *cobra.Command, args []string) {
-		fmt.Println(style.Bold.Render("gt") + " - Gas Town CLI")
-		fmt.Printf("Version:  %s\n", Version)
-		fmt.Printf("Commit:   %s\n", style.Dim.Render(GitCommit))
-		fmt.Printf("Built:    %s\n", style.Dim.Render(BuildTime))
+		commit := resolveCommitHash()
+		branch := resolveBranch()
+
+		if commit != "" && branch != "" {
+			fmt.Printf("gt version %s (%s: %s@%s)\n", Version, Build, branch, shortCommit(commit))
+		} else if commit != "" {
+			fmt.Printf("gt version %s (%s: %s)\n", Version, Build, shortCommit(commit))
+		} else {
+			fmt.Printf("gt version %s (%s)\n", Version, Build)
+		}
 	},
 }
 
 func init() {
 	rootCmd.AddCommand(versionCmd)
 }
+
+func resolveCommitHash() string {
+	if Commit != "" {
+		return Commit
+	}
+
+	if info, ok := debug.ReadBuildInfo(); ok {
+		for _, setting := range info.Settings {
+			if setting.Key == "vcs.revision" && setting.Value != "" {
+				return setting.Value
+			}
+		}
+	}
+
+	return ""
+}
+
+func shortCommit(hash string) string {
+	if len(hash) > 12 {
+		return hash[:12]
+	}
+	return hash
+}
+
+func resolveBranch() string {
+	if Branch != "" {
+		return Branch
+	}
+
+	// Try to get branch from build info (build-time VCS detection)
+	if info, ok := debug.ReadBuildInfo(); ok {
+		for _, setting := range info.Settings {
+			if setting.Key == "vcs.branch" && setting.Value != "" {
+				return setting.Value
+			}
+		}
+	}
+
+	// Fallback: try to get branch from git at runtime
+	cmd := exec.Command("git", "symbolic-ref", "--short", "HEAD")
+	cmd.Dir = "."
+	if output, err := cmd.Output(); err == nil {
+		if branch := strings.TrimSpace(string(output)); branch != "" && branch != "HEAD" {
+			return branch
+		}
+	}
+
+	return ""
+}