tested on ubuntu 15.10
clone meld (meldmerge.org)
git clone https://git.gnome.org/browse/meld
for po-translations
sudo apt-get install itstool
install/update (before close app) meld
sudo python setup.py install --prefix=/usr
find last po-file on https://l10n.gnome.org/vertimus/meld/master/po/ru
wget https://l10n.gnome.org/media/upload/meld-master-po-ru-29086_R1DxSuM.merged.po
backup meld.mo
sudo cp /usr/share/locale/ru/LC_MESSAGES/meld.mo /usr/share/locale/ru/LC_MESSAGES/meld.mo.160126
po (text) -> mo (compiled)
sudo msgfmt meld-master-po-ru-29086_R1DxSuM.merged.po -o /usr/share/locale/ru/LC_MESSAGES/meld.mo