Saute the ginger, garlic and red chilies in the oil overy medium heat for until softened. Add the spices and saute just until fragrant. Lower the heat a little for this step. Be careful not to burn them. If you burn this mixture, throw it out and start over, otherwise, your chutney will be bitter.
Add the diced mangoes, sugar, salt, and vinegar and stir well. Bring it to a boil and reduce to medium-low. Simmer partially covered for 30-40, or until mango is soft and mixture is thickened. It should look like chunky jam.
Remove from heat and allow it to cool. It'll thicken more as it cools and especially after refrigerating.
Store in a glass jar, plastic will work too, just don't use metal. The chutney will keep up to 2 months in the fridge if it lasts that long!