--stdin makes vim complaining

[herrerog]

When running tig --no-walk --stdin < cherry-picks.txt and trying to edit a file by pressing e, with vim, I'm getting:
Vim: Warning: Input is not from a terminal
This is a similar issue as in #1229 but I tried with master and it still happen.

[koutcher]

#1229 correction only targeted readline so it's normal it doesn't work, but I agree, the editor should be fixed as well.