TortoiseGitMerge: Document the missing command line options

Signed-off-by: Sup Yut Sum <ch3cooli@gmail.com>
Document more about create branch / tag

Signed-off-by: Sup Yut Sum <ch3cooli@gmail.com>
Explain push options "Always push to the selected remote archive/branch for this local branch"

Signed-off-by: Sup Yut Sum <ch3cooli@gmail.com>
Update tagopt meaning in Git Remote Settings documentation

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