I had a similar split in a vertical copper pipe. It led to an outside hose bib, but can't recall if I'd absent-mindedly closed the faucet.
Maybe it was a cold north wind, but I didn't want to scare up the necessary hardware. Instead, I took a yarn from a nearby mop, and pressed it into the "breech". Using a Channel-Lock pliers from the opposite side. I then crushed the broken edges together on the yarn.
Instead of "just getting by" for the next 24 hours, the "fix" lasted several years until a visiting plumber rejected my handiwork.
I've saved my work product in spite of his disrespecting my provisional--but long-lived--repair.
