Basic CLI help and error checking for a valid stride

util/checkpoints.pl

@@ -10,6 +10,16 @@ my $perday  = 1152;
 my $hush    = "./src/hush-cli";
 my $gethash = "$hush getblockhash";
 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: $0 X &> checkpoints.txt\n";
+    exit 0;
+}
+
+unless ($stride == int($stride) and $stride >= 0) {
+    print "Invalid stride! Must be an integer > 0\n";
+    exit 1;
+}
 my $count   = 0;
 my $blocks  = qx{$hush getblockcount};
 if($?) {