Refactor SSH commands with SshCommand base class

The SshCommand base class extends BaseCommand and provides the common
pattern of calling startThread with a CommandRunnable that parses
argments and then invokes the real logic.

The new annotation @RequiresCapability can be declared on any concrete
implementation of SshCommand to name a capability the caller must have
before they can run the contained command. This is enforced inside of
the DispatchCommand, which is what handles creating and delegating to
any paticular command implementation.

@AdminCommand is replaced by the new @RequriesCapability annotation,
which is more explicitly declaring the administrate server dependency.

Most existing commands have been ported to this SshCommand base class,
cleaning up a lot of the code. A few special cases still exist such as
StreamEvents or ScpCommand that are not trivial to port, as their start
implementation is well outside of the common pattern.

Plugin authors should be encouraged to extend from SshCommand for the
foreseeable future. I eventually would like to get away from needing
to extend this class, and instead use a simpler interface declaration,
but that is a much bigger change to make with how DispatchCommand and
BaseCommand are connected together.

Change-Id: I4f1de60c6fdeb207197dfccc135b4d532443d5b2

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

@@ -23,13 +23,13 @@ import com.google.gerrit.server.project.ProjectCache;
 import com.google.gerrit.server.project.ProjectState;
 import com.google.gerrit.server.util.IdGenerator;
 import com.google.gerrit.sshd.AdminHighPriorityCommand;
-import com.google.gerrit.sshd.BaseCommand;
+import com.google.gerrit.sshd.SshCommand;
 import com.google.inject.Inject;
 
 import org.apache.sshd.server.Environment;
 import org.kohsuke.args4j.Option;
 
-import java.io.PrintWriter;
+import java.io.IOException;
 import java.text.SimpleDateFormat;
 import java.util.Collections;
 import java.util.Comparator;
@@ -39,7 +39,7 @@ import java.util.concurrent.TimeUnit;
 
 /** Display the current work queue. */
 @AdminHighPriorityCommand
-final class ShowQueue extends BaseCommand {
+final class ShowQueue extends SshCommand {
   @Option(name = "-w", usage = "display without line width truncation")
   private boolean wide;
 
@@ -52,12 +52,11 @@ final class ShowQueue extends BaseCommand {
   @Inject
   private IdentifiedUser currentUser;
 
-  private PrintWriter p;
   private int columns = 80;
   private int taskNameWidth;
 
   @Override
-  public void start(final Environment env) {
+  public void start(final Environment env) throws IOException {
     String s = env.getEnv().get(Environment.ENV_COLUMNS);
     if (s != null && !s.isEmpty()) {
       try {
@@ -66,19 +65,11 @@ final class ShowQueue extends BaseCommand {
         columns = 80;
       }
     }
-
-    startThread(new CommandRunnable() {
-      @Override
-      public void run() throws Exception {
-        parseCommandLine();
-        ShowQueue.this.display();
-      }
-    });
+    super.start(env);
   }
 
-  private void display() {
-    p = toPrintWriter(out);
-
+  @Override
+  protected void run() {
     final List<Task<?>> pending = workQueue.getTasks();
     Collections.sort(pending, new Comparator<Task<?>>() {
       public int compare(Task<?> a, Task<?> b) {
@@ -103,9 +94,9 @@ final class ShowQueue extends BaseCommand {
 
     taskNameWidth = wide ? Integer.MAX_VALUE : columns - 8 - 12 - 8 - 4;
 
-    p.print(String.format("%-8s %-12s %-8s %s\n", //
+    stdout.print(String.format("%-8s %-12s %-8s %s\n", //
         "Task", "State", "", "Command"));
-    p.print("----------------------------------------------"
+    stdout.print("----------------------------------------------"
         + "--------------------------------\n");
 
     int numberOfPendingTasks = 0;
@@ -158,7 +149,7 @@ final class ShowQueue extends BaseCommand {
 
       // Shows information about tasks depending on the user rights
       if (viewAll || (!hasCustomizedPrint && regularUserCanSee)) {
-        p.print(String.format("%8s %-12s %-8s %s\n", //
+        stdout.print(String.format("%8s %-12s %-8s %s\n", //
             id(task.getTaskId()), start, "", format(task)));
       } else if (regularUserCanSee) {
         if (remoteName == null) {
@@ -167,20 +158,18 @@ final class ShowQueue extends BaseCommand {
           remoteName = remoteName + "/" + projectName;
         }
 
-        p.print(String.format("%8s %-12s %-8s %s\n", //
+        stdout.print(String.format("%8s %-12s %-8s %s\n", //
             id(task.getTaskId()), start, "", remoteName));
       }
     }
-    p.print("----------------------------------------------"
+    stdout.print("----------------------------------------------"
         + "--------------------------------\n");
 
     if (viewAll) {
       numberOfPendingTasks = pending.size();
     }
 
-    p.print("  " + numberOfPendingTasks + " tasks\n");
-
-    p.flush();
+    stdout.print("  " + numberOfPendingTasks + " tasks\n");
   }
 
   private static String id(final int id) {