ref: c3cfd06564ab868d1e78bf5fe8fe6fac07202de9
dir: /sys/src/cmd/hgfs/dat.h/
enum {
	MAXPATH = 1024,
	BUFSZ = 1024,
	HASHSZ = 20,
};
typedef struct Revlog Revlog;
typedef struct Revmap Revmap;
typedef struct Revinfo Revinfo;
typedef struct Revtree Revtree;
typedef struct Revnode Revnode;
typedef struct Revfile Revfile;
struct Revmap
{
	int	rev;
	int	p1rev;
	int	p2rev;
	int	baserev;
	int	linkrev;
	uchar	hash[HASHSZ];
	int	flags;
	vlong	hoff;
	vlong	hlen;
	vlong	flen;
	void	*aux;
};
struct Revlog
{
	Ref;
	Revlog	*next;
	char	*path;
	int	ifd;
	int	dfd;
	vlong	ioff;
	int	nmap;
	Revmap	*map;
	int	tfd;
	int	tid;
};
struct Revnode
{
	char	*name;
	uchar	*hash;
	uvlong	path;
	Revnode	*up;
	Revnode	*next;
	Revnode	*down;
	Revnode *before;
	char	mode;
};
struct Revinfo
{
	uchar	chash[HASHSZ];
	uchar	mhash[HASHSZ];
	char	*who;
	char	*why;
	ulong	when;
	vlong	logoff;
	vlong	loglen;
};
struct Revtree
{
	Ref;
	int	level;
	Revnode	*root;
};
struct Revfile
{
	int	level;
	Revinfo	*info;
	Revtree	*tree;
	Revnode	*node;
	Revlog	*rlog;
	char	*buf;
	int	fd;
	int	doff;	/* length of metadata to skip */
};
uchar nullid[HASHSZ];