rev-list --boundary

With the new --boundary flag, the output from rev-list includes
the UNINTERESING commits at the boundary, which are usually not
shown.  Their object names are prefixed with '-'.

For example, with this graph:

              C side
             /
	A---B---D master

You would get something like this:

	$ git rev-list --boundary --header --parents side..master
	D B
        tree D^{tree}
        parent B
        ... log message for commit D here ...
        \0-B A
        tree B^{tree}
        parent A
        ... log message for commit B here ...
        \0

Signed-off-by: Junio C Hamano <junkio@cox.net>

revision.h

@@ -6,6 +6,7 @@
 #define TREECHANGE	(1u<<2)
 #define SHOWN		(1u<<3)
 #define TMP_MARK	(1u<<4) /* for isolated cases; clean after use */
+#define BOUNDARY	(1u<<5)
 
 struct rev_info;
 
@@ -32,7 +33,8 @@ struct rev_info {
 			blob_objects:1,
 			edge_hint:1,
 			limited:1,
-			unpacked:1;
+			unpacked:1,
+			boundary:1;
 
 	/* special limits */
 	int max_count;