I had a leak about 1" above the slab on a piece of 3/4 copper that the sheet rock guys had put a nail in and it finally rusted off. There was a tee about an inch above the hole. No space at all.
I took a 3/4" slip coupling, cut about a third of it out lengthwise and bevelled the edges so it would snap around the pipe when pushed. I cleaned and tinned the coupling and the pipe. Pushed it on and soldered it. Voila!