Change to lambda expressions

Signed-off-by: Sup Yut Sum <ch3cooli@gmail.com>
Do not show Pull menu button if still detached HEAD after checkout

Signed-off-by: Sup Yut Sum <ch3cooli@gmail.com>
Fixed issue #2109: Checkout Tag without creating Branch - Remove Pull Option

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