Automatically set /dev/tty as STDIN on execute action

https://github.com/junegunn/fzf/issues/1360#issuecomment-788178140

  # Redirect /dev/tty to suppress "Vim: Warning: Input is not from a terminal"
  ls | fzf --bind "enter:execute(vim {} < /dev/tty)"

  # With this change, we can omit "< /dev/tty" part
  ls | fzf --bind "enter:execute(vim {})"

src/terminal.go

@@ -1723,7 +1723,7 @@ func (t *Terminal) executeCommand(template string, forcePlus bool, background bo
 	command := t.replacePlaceholder(template, forcePlus, string(t.input), list)
 	cmd := util.ExecCommand(command, false)
 	if !background {
-		cmd.Stdin = os.Stdin
+		cmd.Stdin = tui.TtyIn()
 		cmd.Stdout = os.Stdout
 		cmd.Stderr = os.Stderr
 		t.tui.Pause(true)