If you're careful you should be able to undo the hose and reattach it without bleeding.
I shortened the hose on some Hayes Discs last night and had no problems. I've also done this to Magura rim and disc brakes with no issues.
- Undo the nut at the lever end - there will be some brake fluid leakage at this point, though only a small amount.
- Make sure that the end of the master cylinder/brake reservoir is facing up. Also make sure you don't press the lever at this point!
- Thread the hose through the guides on the frame.
- Cut the end of the hose to remove the compression olive.
- Put the new olive on - making sure that you have the nut and any plastic cover already on the hose (they won't fit over the olive once it's on! I know I've done this!)
- Slide the end of the hose into the brake lever and do up the nut.
Hopefully (If you've been careful) no air will have got into the system, and you won't need to bleed it.