add gc greedy

btv

@@ -9,6 +9,7 @@ import json
 import os
 import shlex
 import sys
+import time
 
 CONFIG = "/etc/btv/config.ini"
 LOCKFILE = "/run/lock/btv/serialization.lock"
@@ -487,8 +488,27 @@ def do_stream(args):
 def do_gc(args=None):
 	"""
 	Drops old snapshots.
+	
+	If the only arg is "greedy", drops ALL snapshots except the youngest
+	Rank 2.
 	"""
 	
+	if args and "greedy" in args:
+		newest = list_snapshots(2)[-1]
+		
+		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()
+		
+		else:
+			print("!!! no Rank 2 snapshot exists")
+			sys.exit(1)
+	
+	else:
 		counts = [0, 0, 0] # Rank 0, 1, 2
 		limits = [
 			cfg.getint("gc", "rank_0_count"),
@@ -537,6 +557,9 @@ Verbs:
   
   gc
     Drops old local snapshots based on garbage collector settings.
+  
+  gc greedy
+    Drop ALL snapshots except the newest Rank 2.
 """.format(cmd=sys.argv[0]))
 
 if __name__ == "__main__":