Mark strings for translation in lib/index.tcl that were seemingly
left behind by 700e560 ("git-gui: Mark forgotten strings for
translation.", 2008-09-04) which marks string in do_revert_selection
procedure.
These strings are passed to unstage_help and add_helper procedures.
Signed-off-by: Vasco Almeida <vascomalmeida@sapo.pt> Signed-off-by: Junio C Hamano <gitster@pobox.com>