read input from stdin or fd special file

[milahu]

this should work

$ echo '{}' | nix-editor --val 1 /dev/stdin a
error: reading '/dev/stdin': No such file

$ echo '{}' | nix-editor --val 1 - a
error: reading '-': No such file

$ nix-editor --val 1 <(echo '{}') a
error: reading '/dev/fd/63': No such file

this works with standard CLI tools like cat

$ echo foo | cat /dev/stdin | head -c1
f

$ echo foo | cat - | head -c1
f

$ cat <(echo foo) | head -c1
f

[vlinkz]

Fixed in 188f6f8, thanks :)