[a1369209993]

> For example, you can't do `gpg --decrypt foo.txt.gpg | nano | gpg --encrypt` because keyboard input on the console is handled through stdin.

I actually had a alias at one point that did something along the lines of (IIRC):

  | editor | -> | editor -i /dev/fd/3 -o /dev/fd/4 3<&0 4>&1 0<&2 1>&2 |

Since stderr (aka &2 aka /dev/pts/whatever) is opened read-write, you can dup it onto stdin to recover the terminal. Ideally, every editor should just support reading from stdin, interacting via stderr[0], and writing to stdout as a command line option though.

Edit: 0: or /dev/tty as jclulow suggested.