Agree with just riding with the big need of periodic inspection for crack starts. Steel is wonderful in that unless seriously overheated/cooled quickly its cracks tend to become more tears that slow down. Giving one time to see then while a majority of the tube's diameter to still be intact.

I would fix this bike if it were me only because I can, a top tube replacement being what i anticipate. If on the road, and it started to crack, and had "facilities" I'd sandwich the dent portion and still replace the tube when home. All this dependent on my liking the bike and wanting to continue to ride it for years to come. If not scrap it after replacing it after it cracks.

Here's a shot of a friends old 531 frame that broke on the down tube about the bottle cage clamps, yes not the braze ons... The rider tightly wrapped some beer can "splints" with hose clamps around it and continued the cross country bike ride. I ended up repairing it as it was sentimental to the rider, a friend. Otherwise it would have been tossed. Andy.