Repair tiny hole/scratch in copper pipe

You could lay a coating of solder on the pipe, preferably a silver bearing alloy, but you would have to drain that pipe and have "it bone dry". You could clean the copper, drop the boiler pressure to near zero so the drip stops and lay on a coat of fast dry epoxy. These are 2 ideas, hope this helps Also, Home DEpot sells a 1/2" copper compression X compression repair coupling in a 12 lingth length.

I have not seen patches hold up on copper. What I find best is to cut it at the hole and sweat a coupler on. It must be dry when you do the soldering or it will leak.

I've had some success with this stuff - it's basically a fiber tape soaked in something like gorilla glue. But I'd only consider it a temporary repair. the right way is to cut the pipe and solder in a coupler.

A common option in the UK (dunno if they are available in other countries) for fixing damaged copper pipes is a compression repair coupler. The coupling has compression fittings on both ends only one of which has a depth stop, so after cutting the pipe you can slide the fitting onto one pipe and then slide it back onto the other with minimal movement of the pipe ends.

What I've done in the past is to saw a coupler in half lengthwise, use a file to remove the center ridge (unless you can find a "repair coupler" that lacks the ridge), thoroughly clean and flux the pipe and inside of the coupler, tie half of the coupler on with bare copper wire (after cleaning/fluxing it), then (after making sure the pipe is perfectly dry inside) sweat-solder the assembly. Of course, this requires a couple of inches clearance all around to allow soldering safely.

Anymore, I'd just buy a SharkBite coupling, cut the pipe at the defect, then install that coupling.

If the pipe sizes in your country do telescoping, then the next size up in copper pipe will fit exactly over your pipe as a sleeve. I would cut a small section of sleeve, removing the scratched section, and solder the sleeve into place.

An option I haven't seen suggested, but one that I've seen several times and employed at least once myself, is to use a clamp to secure a rubber gasket. There are commercially made clamps

or you can cobble your own with a piece of inner tube and a hose clamp.

I wouldn't recommend these for concealed use, but where the patch will be accessible I think they're fine, and probably code-accepted in at least some cases.