^J's break copy-pasting of multi-line command examples into terminal

[simonmichael]

Multi-line commands like https://hledger.org/install.html#build-in-a-source-checkout don't copy-paste into terminal successfully, because you get ^J between lines instead of newline. I see this with safari and brave on mac, but I don't remember it happening before.

rust-lang/mdBook#2506

[simonmichael]

Aankhen> I’m not seeing this on Windows with Firefox. I tried pasting into both Notepad and Emacs. No ^J.