I have a 20 amp breaker and 12 gauge wire running out to a shed that is wired with 14 gauge wire. The shed has 3 receptacle, 1 light switch and 1 light receptacle. Is this safe?
You could install a pony panel in the garage. Where I live, the panel needs to be more than 3 feet above the ground, but within 6 feet of where the power enters the structure. Please check you local electrical code. You would install a small breaker panel with a 20A disconnect and then 15A breakers for your circuits on 14 Ga wire. This would allow you to have your light on one local circuit and the outlets on other circuits, so, if you trip one of the outlet circuits, the light will stay on.
You can use a single phase, 120V panel with 4 or 6 slots. One of the slots would be your 20A disconnect; a regular breaker with the "load" connected to the supply. It looks a little funny, but it will work and it should meet code.