This configures ProxyOptions for all libgit2 Checkout functions when
cloning and configures the options based on current environment
settings using the git2go.ProxyTypeAuto option.
Refs: #131
Signed-off-by: Robert Clarke <rob@robertandrewclarke.com>
Co-authored-by: Aurélien GARNIER <aurelien.garnier@atos.net>