feat: add RestoreGit to restore git identity from snapshot

Author: fullstackjam

internal/snapshot/capture.go

@@ -1,6 +1,7 @@
 package snapshot
 
 import (
+	"fmt"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -9,6 +10,7 @@ import (
 	"time"
 
 	"github.com/openbootdotdev/openboot/internal/macos"
+	"github.com/openbootdotdev/openboot/internal/system"
 )
 
 // Capture orchestrates a full environment snapshot.
@@ -406,6 +408,29 @@ func CaptureGit() (*GitSnapshot, error) {
 	return snap, nil
 }
 
+// RestoreGit writes global git user.name and user.email from a snapshot, skipping values already configured.
+func RestoreGit(git GitSnapshot) error {
+	existingName, existingEmail := system.GetExistingGitConfig()
+
+	if git.UserName == "" && git.UserEmail == "" {
+		return nil
+	}
+
+	if existingName == "" && git.UserName != "" {
+		if err := system.RunCommand("git", "config", "--global", "user.name", git.UserName); err != nil {
+			return fmt.Errorf("failed to restore git user.name: %w", err)
+		}
+	}
+
+	if existingEmail == "" && git.UserEmail != "" {
+		if err := system.RunCommand("git", "config", "--global", "user.email", git.UserEmail); err != nil {
+			return fmt.Errorf("failed to restore git user.email: %w", err)
+		}
+	}
+
+	return nil
+}
+
 var devToolCommands = []struct {
 	name string
 	args []string