Heat oil and ginger in a large pot until they start to sizzle and become fragrant, a minute or so. Add tomato sauce, curry powder, chickpeas, and coconut milk; bring to a simmer. Add spinach; return to simmer to heat through, a couple of minutes longer. Adjust seasoning, including salt and pepper to taste. Ladle into bowls of rice and serve. Garnish with cilantro if desired.