Default to REAL TLDs in nomulus list_domains command

This is what you want most of the time when you're running the command to
see recent domains, as this will list all the real billable domains and
exclude the prober ones.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=217603275

java/google/registry/tools/ListDomainsCommand.java

@@ -15,11 +15,14 @@
 package google.registry.tools;
 
 import static com.google.common.base.Preconditions.checkArgument;
+import static google.registry.model.registry.Registries.getTldsOfType;
+import static google.registry.util.CollectionUtils.isNullOrEmpty;
 
 import com.beust.jcommander.Parameter;
 import com.beust.jcommander.Parameters;
 import com.google.common.base.Joiner;
 import com.google.common.collect.ImmutableMap;
+import google.registry.model.registry.Registry.TldType;
 import google.registry.tools.server.ListDomainsAction;
 import java.util.List;
 
@@ -29,8 +32,7 @@ final class ListDomainsCommand extends ListObjectsCommand {
 
   @Parameter(
       names = {"-t", "--tld", "--tlds"},
-      description = "Comma-delimited list of top-level domain(s) to list second-level domains of.",
-      required = true)
+      description = "Comma-delimited list of TLDs to list domains on; defaults to all REAL TLDs.")
   private List<String> tlds;
 
   @Parameter(
@@ -47,6 +49,10 @@ final class ListDomainsCommand extends ListObjectsCommand {
   /** Returns a map of parameters to be sent to the server (in addition to the usual ones). */
   @Override
   ImmutableMap<String, Object> getParameterMap() {
+    // Default to all REAL TLDs if not specified.
+    if (isNullOrEmpty(tlds)) {
+      tlds = getTldsOfType(TldType.REAL).asList();
+    }
     String tldsParam = Joiner.on(',').join(tlds);
     checkArgument(tldsParam.length() < 1024, "Total length of TLDs is too long for URL parameter");
     return ImmutableMap.of("tlds", tldsParam, "limit", maxDomains);