Update libgit2

Signed-off-by: Sven Strickroth <email@cs-ware.de>
Fixed issue #2385: 'Mail' - 'Use configured server' & 'none'... seems can not be localized

Signed-off-by: Yue Lin Ho <b8732003@student.nsysu.edu.tw>
Update warning for old Git for Windows versions

Signed-off-by: Sven Strickroth <email@cs-ware.de>
Update Git for Windows website

Signed-off-by: Sven Strickroth <email@cs-ware.de>
Better distribute version checks over all week days

Signed-off-by: Sven Strickroth <email@cs-ware.de>
Fixed issue #2356: Rebase dialog should also auto-link to issue tracker

Signed-off-by: Sven Strickroth <email@cs-ware.de>
Can retry failed clone

Signed-off-by: Sup Yut Sum <ch3cooli@gmail.com>