Clone options structure

Use zeros to indicate default settings. It's easiest to use the GIT_CLONE_OPTIONS_INIT macro:

git_clone_options opts = GIT_CLONE_OPTIONS_INIT;

• checkout_opts is options for the checkout step. To disable checkout, set the checkout_strategy to GIT_CHECKOUT_DEFAULT.
• bare should be set to zero to create a standard repo, non-zero for a bare repo
• fetch_progress_cb is optional callback for fetch progress. Be aware that this is called inline with network and indexing operations, so performance may be affected.
• fetch_progress_payload is payload for fetch_progress_cb

** "origin" remote options: **

• remote_name is the name given to the "origin" remote. The default is "origin".
• pushurl is a URL to be used for pushing. NULL means use the fetch url.
• fetch_spec is the fetch specification to be used for fetching. NULL results in the same behavior as GIT_REMOTE_DEFAULT_FETCH.
• push_spec is the fetch specification to be used for pushing. NULL means use the same spec as for fetching.
• cred_acquire_cb is a callback to be used if credentials are required during the initial fetch.
• cred_acquire_payload is the payload for the above callback.
• transport_flags is flags used to create transport if no transport is provided.
• transport is a custom transport to be used for the initial fetch. NULL means use the transport autodetected from the URL.
• remote_callbacks may be used to specify custom progress callbacks for the origin remote before the fetch is initiated.
• remote_autotag may be used to specify the autotag setting before the initial fetch. The default is GIT_REMOTE_DOWNLOAD_TAGS_ALL.
• checkout_branch gives the name of the branch to checkout. NULL means use the remote's HEAD.