feat(cli): add update subcommand for in-place self-update

internal/cli/update.go

@@ -0,0 +1,54 @@
+package cli
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+
+	"github.com/spf13/cobra"
+)
+
+const installURL = "https://raw.githubusercontent.com/lukaszraczylo/harness-sync/main/install.sh"
+
+// NewUpdate returns the `update` subcommand. It downloads and installs the
+// latest harness-sync release into the same directory the running binary
+// lives in.
+func NewUpdate() *cobra.Command {
+	var (
+		dryRun bool
+		dir    string
+	)
+	cmd := &cobra.Command{
+		Use:   "update",
+		Short: "Download and install the latest harness-sync release in place",
+		RunE: func(cmd *cobra.Command, _ []string) error {
+			if dir == "" {
+				exe, err := os.Executable()
+				if err != nil {
+					return fmt.Errorf("resolve current binary path: %w", err)
+				}
+				resolved, err := filepath.EvalSymlinks(exe)
+				if err == nil {
+					exe = resolved
+				}
+				dir = filepath.Dir(exe)
+			}
+			pipeline := fmt.Sprintf("curl -fsSL %q | INSTALL_DIR=%q bash", installURL, dir)
+			if _, err := fmt.Fprintf(cmd.OutOrStdout(), "Installing latest harness-sync into %s\n", dir); err != nil {
+				return err
+			}
+			if dryRun {
+				_, err := fmt.Fprintln(cmd.OutOrStdout(), pipeline)
+				return err
+			}
+			sh := exec.Command("/bin/bash", "-c", pipeline)
+			sh.Stdout = cmd.OutOrStdout()
+			sh.Stderr = cmd.ErrOrStderr()
+			return sh.Run()
+		},
+	}
+	cmd.Flags().BoolVar(&dryRun, "dry-run", false, "print the install command without executing it")
+	cmd.Flags().StringVar(&dir, "install-dir", "", "override install directory (default: dir of running binary)")
+	return cmd
+}