custom libgit2 vapi

[CCode (cheader_filename = "git2.h")]
namespace Git {
    [Compact]
    [CCode (cname = "git_repository")]
    public class Repository {

        public static int init (out Repository repo, string path, bool is_bare);
        public static int open (out Repository repo, string path);
        public static int open_bare (out Repository repo, string bare_path);
        public static int wrap_odb (out Repository repo, Odb? odb);

        [CCode (instance_pos = -1)]
        public int head (out Reference reference);
        public bool head_detached();
        public bool head_unborn();
        public bool is_bare();
        public bool is_empty();
        public string path();
        public string workdir();
        public int set_workdir (string wd, bool update_link);

    }

    [Compact]
    [CCode (cname = "git_reference")]
    public class Reference {
        public int cmp (Reference r);
    }

    [Compact]
    [CCode (cname = "git_reflog")]
    public class Reflog {
        public static int read (out Reflog log, Repository repo, string name);

        [CCode (cname = "git_reflog_entry_byindex")]
        public Entry get (size_t index);
        public Entry entry_byindex (size_t index);

        public size_t size {
            [CCode (cname = "git_reflog_entrycount")]
            get;
        }

        [Compact]
        [CCode (cname = "git_reflog_entry", free_function = "git_reflog_entry__free")]
        public class Entry {
            [CCode (cname = "git_reflog_entry__alloc")]
            public Entry();
            public Signature committer();
            public string message();
        }
    }

    [Compact]
    [CCode (cname = "git_signature")]
    public class Signature {

    }

    [Compact]
    [CCode (cname = "git_odb")]
    public class Odb {}
}