I had an injector line start leaking, and I went to the dealer to get a new line, and it wasn't even available. The shop foreman said to just braze it, that is what they did all the time, and then he grabbed it and brazed it for me in a couple of minutes and I was on my way.It lasted for as long as I used the machine,and afterwards I used it on a generator, too, until the motor blew up.
I like brazing stuff, for some reason it is relaxing to me. I have brazed hydraulic tubing and it held up as good as new except in one case where the crack in the tube was right at a fitting on a pump which had a vibration. It lasted about a year and cracked again. An injector line should be fine, especially if it is from an old school diesel that probably makes less than 3000 psi. I would try to fix the problem that caused the hole, usually a clamp is gone or loose and two lines rubbed each other. Flush it out good when you are done and the idea of reinforcing the area with wire sounds good, but I have never tried that.