Allow custom starting height to generate checkpoint data

util/checkpoints.pl

@@ -13,6 +13,7 @@ my $stride  = shift || 1000;
 if ($stride =~ m/help/) {
     print "To generate checkpoint data every 1000 blocks: $0 &> checkpoints.txt\n";
     print "To generate checkpoint data every X blocks: $0 X &> checkpoints.txt\n";
+    print "To generate checkpoint data every X blocks starting at height Y: $0 X Y &> checkpoints.txt\n";
     exit 0;
 }
 
@@ -20,6 +21,13 @@ unless ($stride == int($stride) and $stride >= 0) {
     print "Invalid stride! Must be an integer > 0\n";
     exit 1;
 }
+my $start_height = shift || 0;
+
+unless ($start_height == int($start_height) and $start_height >= 0) {
+    print "Invalid start_height! Must be an integer > 0\n";
+    exit 1;
+}
+
 my $count   = 0;
 my $blocks  = qx{$hush getblockcount};
 if($?) {
@@ -35,7 +43,7 @@ print "// Generated at $now via hush3 util/checkpoints.pl by Duke Leto\n";
 
 while (1) {
 	$count++;
-	my $block = $stride*$count;
+	my $block = $start_height + $stride*$count;
 	if ($block > $blocks) {
 		$last = $stride*($count-1);
         #print "last checkpointed block=$last\n";