Add "aggressive" option to ssh command "GC"

When triggering a garbage collection through ssh it can be specified
whether to run an aggressive garbage collection or not.

Change-Id: Icfecc69915870289f5957912d3d53348f21a83f7

Documentation/cmd-gc.txt

@@ -8,6 +8,7 @@ gerrit gc - Run the Git garbage collection
 'ssh' -p <port> <host> 'gerrit gc'
   [--all]
   [--show-progress]
+  [--aggressive]
   <NAME> ...
 --
 
@@ -44,6 +45,9 @@ This command is intended to be used in scripts.
 --show-progress::
 	If specified progress information is shown.
 
+--aggressive::
+	If an aggressive garbage collection should be done.
+
 == EXAMPLES
 
 Run the Git garbage collection for the projects 'myProject' and

gerrit-sshd/src/main/java/com/google/gerrit/sshd/commands/GarbageCollectionCommand.java

@@ -46,6 +46,9 @@ public class GarbageCollectionCommand extends SshCommand {
   @Option(name = "--show-progress", usage = "progress information is shown")
   private boolean showProgress;
 
+  @Option(name = "--aggressive", usage = "run aggressive garbage collection")
+  private boolean aggressive;
+
   @Argument(index = 0, required = false, multiValued = true, metaVar = "NAME",
       usage = "projects for which the Git garbage collection should be run")
   private List<ProjectControl> projects = new ArrayList<>();
@@ -85,7 +88,8 @@ public class GarbageCollectionCommand extends SshCommand {
     }
 
     GarbageCollectionResult result =
-        garbageCollectionFactory.create().run(projectNames, showProgress ? stdout : null);
+        garbageCollectionFactory.create().run(projectNames, aggressive,
+            showProgress ? stdout : null);
     if (result.hasErrors()) {
       for (GarbageCollectionResult.Error e : result.getErrors()) {
         String msg;