--- emerge.orig	2005-02-07 18:56:00.000000000 -0700
+++ emerge.new	2005-02-07 23:38:40.521975872 -0700
@@ -611,21 +611,23 @@
 if "--update" in myopts:
 	add.extend(["selective","empty"])
 if "--emptytree" in myopts:
-	add.extend(["empty"])
-	sub.extend(["selective"])
+	add.append("empty")
+	sub.append("selective")
 if "--nodeps" in myopts:
-	sub.extend(["recurse"])
+	sub.append("recurse")
 if "--noreplace" in myopts:
-	add.extend(["selective"])
+	add.append("selective")
 if "--deep" in myopts:
-	add.extend(["deep"])
+	add.append("deep")
 if "--selective" in myopts:
-	add.extend(["selective"])
+	add.append("selective")
 if myaction in ["world","system"]:
-	add.extend(["selective"])
+	add.append("selective")
+	if myaction == "system":
+		add.append("rebuild")
 elif myaction in ["depclean"]:
-	add.extend(["empty"])
-	sub.extend(["selective"])
+	add.append("empty")
+	sub.append("selective")
 for x in add:
 	if (x not in myparams) and (x not in sub):
 		myparams.append(x)
@@ -903,16 +905,38 @@
 	
 		merging=1
 		if addme:
-		# this is where we add the node to the list of packages to merge
+			# this is where we add the node to the list of packages to merge
+			if "rebuild" in myparams:
+
+				# in rebuild mode, we will ignore that the package exists if it has a non-empty REBUILD file in its
+				# /var/db/pkg/ directory. This way, a non-empty REBUILD file will cause the package to be rebuilt.
+				
+				dorebuild=vardbapi.aux_get(mykey, ["REBUILD"])
+				if dorebuild == []:
+					#package really not on system (aux_get returns [] if its own cpv_exists() call fails
+					exists = 0
+				elif dorebuild[0] == "":
+					#REBUILD flag is not there, so we view it
+					exists = 1
+				else:
+					#REBUILD flag is there, so we pretend package isn't installed
+					exists = 0
+			else:
+				#perform this call once to improve performance
+				exists = vardbapi.cpv_exists(mykey)
+
+
+			# this is where we add the node to the list of packages to merge
 			if not myparent:
+			
 				# command-line specified or part of a world list...
-				if ("self" not in myparams) or (("selective" in myparams) and vardbapi.cpv_exists(mykey)):
-					# the package is on the system, so don't merge it.
+				if ("self" not in myparams) or (("selective" in myparams) and exists):
 					merging=0
-			elif ("selective" in myparams) and vardbapi.cpv_exists(mykey):
+			
+			elif ("selective" in myparams) and exists:
 				merging=0
 
-			if (merging==0 and "--newuse" in myopts and vardbapi.cpv_exists(mykey)):
+			if (merging==0 and "--newuse" in myopts and exists):
 				iuses=string.split(portage.portdb.aux_get(mykey, ["IUSE"])[0])
 				old_use=string.split(vardbapi.aux_get(mykey, ["USE"])[0])
 				now_use=string.split(self.pkgsettings["USE"])