stat_tracking_info(): clear object flags used during counting

When left-right traversal counts the commits in a diverged history, it
leaves the flags in the commits smudged, and we need to clear them before
we return.  Otherwise the caller cannot inspect other branches with this
function again.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

revision.h

@@ -11,6 +11,7 @@
 #define ADDED		(1u<<7)	/* Parents already parsed and added? */
 #define SYMMETRIC_LEFT	(1u<<8)
 #define TOPOSORT	(1u<<9)	/* In the active toposort list.. */
+#define ALL_REV_FLAGS	((1u<<10)-1)
 
 struct rev_info;
 struct log_info;