Git: Fix popup message for merge

Change-Id: Ie3ef79343b84d615255b70b786347c57511c3309
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: André Hartmann <aha_1980@gmx.de>
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@digia.com>
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>