Remove insane overlapping bit ranges from epoch.c

..and move the DUPCHECK to rev-list.c since both the merge-order and the
upcoming topo-sort get confused by dups.

epoch.c

@@ -582,14 +582,8 @@ int sort_list_in_merge_order(struct commit_list *list, emitter_func emitter)
 	int action = CONTINUE;
 	struct commit_list *reversed = NULL;
 
-	for (; list; list = list->next) {
-		struct commit *next = list->item;
-
-		if (!(next->object.flags & DUPCHECK)) {
-			next->object.flags |= DUPCHECK;
-			commit_list_insert(list->item, &reversed);
-		}
-	}
+	for (; list; list = list->next)
+		commit_list_insert(list->item, &reversed);
 
 	if (!reversed)
 		return ret;

epoch.h

@@ -10,12 +10,12 @@ typedef int (*emitter_func) (struct commit *);
 
 int sort_list_in_merge_order(struct commit_list *list, emitter_func emitter);
 
-#define UNINTERESTING   (1u<<2)
-#define BOUNDARY        (1u<<3)
-#define VISITED         (1u<<4)
-#define DISCONTINUITY   (1u<<5)
-#define DUPCHECK        (1u<<6)
-#define LAST_EPOCH_FLAG (1u<<6)
+/* Low bits are used by rev-list */
+#define UNINTERESTING   (1u<<10)
+#define BOUNDARY        (1u<<11)
+#define VISITED         (1u<<12)
+#define DISCONTINUITY   (1u<<13)
+#define LAST_EPOCH_FLAG (1u<<14)
 
 
 #endif	/* EPOCH_H */

rev-list.c

@@ -8,7 +8,8 @@
 #define SEEN		(1u << 0)
 #define INTERESTING	(1u << 1)
 #define COUNTED		(1u << 2)
-#define SHOWN		(LAST_EPOCH_FLAG << 2)
+#define SHOWN		(1u << 3)
+#define DUPCHECK	(1u << 4)
 
 static const char rev_list_usage[] =
 	"usage: git-rev-list [OPTION] commit-id <commit-id>\n"
@@ -485,6 +486,9 @@ int main(int argc, char **argv)
 		commit = get_commit_reference(arg, flags);
 		if (!commit)
 			continue;
+		if (commit->object.flags & DUPCHECK)
+			continue;
+		commit->object.flags |= DUPCHECK;
 		insert(commit, &list);
 	}