feat: refactor requirements.go

cmd/gogitlabber/requirements.go

@@ -0,0 +1,15 @@
+package main
+
+import (
+	"fmt"
+	"os/exec"
+)
+
+// verify if git is available
+func verifyGitAvailable() error {
+	_, err := exec.LookPath("git")
+	if err != nil {
+		return fmt.Errorf("git is not installed or not in PATH: %w", err)
+	}
+	return nil
+}