git-cli doesn't support http connection timeout, so we cannot set short
30s connection timeout on git fetch. We don't want to put operation
timeout that short because intial git clone can take pretty long.
go-git does expose http client but only globally and is less efficient than cli. So as a hack, just fetch remote server to check if knot is available and is valid git remote server
Signed-off-by: Seongmin Lee git@boltless.me