Add btv gc NUMBER command

btv

@@ -327,7 +327,6 @@ def do_create(args):
 	## do optional processing
 	##
 	if snapshot.rank == 2:
-		
 		## snapshot serialization
 		# if there's a previous Rank 2 snapshot, compute a diff against it
 		# if not or if the process fails, demote this snap to Rank 1
@@ -493,23 +492,42 @@ def do_gc(args=None):
 	Drops old snapshots.
 	
 	If the only arg is "greedy", drops ALL snapshots except the youngest
-	Rank 2.
+	Rank 2. If it's a number, drops that many oldest snapshots.
 	"""
 	
-	if args and "greedy" in args:
-		newest = list_snapshots(2)[-1]
+	if args: 
+		if args[0] == "greedy":
+			newest = list_snapshots(2)[-1]
 			
-		if newest:
-			print(">>> Dropping all snapshots except the newest Rank 2 in 5 s...")
-			time.sleep(5)
+			if newest:
+				print(">>> Dropping all snapshots except the newest Rank 2 in 5 s...")
+				time.sleep(5)
 				
-			for snap in list_snapshots():
-				if snap.name != newest.name:
-					snap.drop()
+				for snap in list_snapshots():
+					if snap.name != newest.name:
+						snap.drop()
+			
+			else:
+				print("!!! no Rank 2 snapshot exists")
+				sys.exit(1)
 		
 		else:
-			print("!!! no Rank 2 snapshot exists")
-			sys.exit(1)
+			try:
+				count = int(args[0])
+			except ValueError:
+				print("!!! %s is not a count of snapshots to delete" %(args[0]))
+				sys.exit(1)
+			
+			snaps = list_snapshots()[:count]
+			
+			for snap in snaps:
+				print("   %d %s %s" %(snap.rank, snap.name, ", ".join(snap.notes)))
+			
+			print(">>> These snapshots will be dropped in 5 s...")
+			time.sleep(5)
+			
+			for snap in snaps:
+				snap.drop()
 	
 	else:
 		counts = [0, 0, 0] # Rank 0, 1, 2
@@ -565,6 +583,9 @@ Verbs:
   
   gc greedy
     Drop ALL snapshots except the newest Rank 2.
+  
+  gc COUNT
+    Drop COUNT oldest snapshots.
 """.format(cmd=sys.argv[0]))
 
 if __name__ == "__main__":