I did a professional grade job destroying my brake lines trying to remove them once, if i recall correctly, I had two diffs, and had significant trouble undoing the 6" section of rubber hose, on one the only way it was coming out was to cut the line, but i needed the rubber one and no one would sell one minus a diff locally, so I cut the steel part of the line instead, went to my nearest wreckers, watched them (a little rough) pull the brake line off the car for me, don't think it cost me more then $20. being i was stripping and rebuilding the car anyway this wasn't an inconvenience.
I highly suggest buying a new brake line, its by far the safest option and as stated brake lines get put under an immense amount of pressure, i personally wouldn't even take the risk of brazing a section back in because of the possibility it may blow out or something..
Oh.. the big thing i've just noticed.. i think the last 3 people may have somehow missed.. if you have a rust hole in your brake line i think its pretty safe to say its f***ed and you need a new one. as i said it will be well under $50 for the long one that runs from the MC to your diff, so it's not a big cost for the piece of mind of having it done properly. not to mention even if you could patch it up sufficiently, what are the chances it ISN'T badly rusted elsewhere that may give way in a few months? personally with the pressure in a brake system (and the fact you trust your life with them..) i would NOT be taking any chances with it. the smallest leak could leave you with no brakes.. and i can think of many places i would hate for this to happen (busy street, down hill @ 100km/h, even reversing out of a car park or something..)
Go pick up another second hand brake line (in good condition) or try get an aftermarket one, whatever, just replace it, do it properly and be done with it for another what, 5 years?
good luck mate!
just thinking too.. IMO a simliar situation would be like cutting a square section from your tire.. from the outside, through to the inside.. then patching said section with squares of rubber, and a sh*t tonne of sikaflex or something, it MIGHT work, for a while.. but its far from safe
EDIT: back to the rust thing.. how the hell did you get a rust hole in your line?
is it from the inside? did you somehow get water in your brake fluid or something? if so this could become a pretty big problem.. may be worth checking the condition of all of your brake lines while you're there.. as i said i'd hate nothing more then to spring a leak in my brake system, to stop and think i've actually blown out a seal on the MC, brake fluid went everywhere and the car had no brakes, 15 ks from home, through town down hills and crap riding gears and the handbrake to prevent going to fast and so i could actually bloody stop. my poor baby :'(