Handle libgit exception when calling GitRev::GetAction()

Signed-off-by: Sup Yut Sum <ch3cooli@gmail.com>
Cleanup: Drop unused gitpath parameter from (S|G)etConfig-methods

Signed-off-by: Sven Strickroth <email@cs-ware.de>
CreateRepository: Do not warn for non-empty folder if non-bare

If the folder already includes a .git folder, libgit2 complains and a rollback can easily be done by removing the .git folder.

(fixes issue #1743)

Signed-off-by: Sven Strickroth <email@cs-ware.de>