Makefile: add "po-update" rule to update po/XX.po
Since there is no longer a "po/git.pot" file in tree, a l10n team leader
has to run several commands to update their "po/XX.po" file:
$ make pot
$ msgmerge --add-location --backup=off -U po/XX.po po/git.pot
To make this process easier, add a new rule so that l10n team leaders
can update their "po/XX.po" with one command. E.g.:
$ make po-update PO_FILE=po/zh_CN.po
Signed-off-by: Jiang Xin <zhiyou.jx@alibaba-inc.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>