Rewrite our build as modular maven components

This refactoring splits the code up into different components, with
their own per-component CLASSPATH.  By moving all of our classes
into isolated components we can better isolate the classpaths and
try to avoid unexpected dependency problems.  It also allows us to
more clearly define which components are used by the GWT UI and
thus must be compiled under GWT, and which components are run on
the server and can therefore use more of the J2SE API.

Change-Id: I833cc22bacc5655d1c9099ed7c2b0e0a5b08855a
Signed-off-by: Shawn O. Pearce <sop@google.com>

gerrit-sshd/src/main/java/com/google/gerrit/sshd/NoShell.java

@@ -0,0 +1,67 @@
+// Copyright (C) 2008 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.sshd;
+
+import org.apache.sshd.server.ShellFactory;
+import org.eclipse.jgit.lib.Constants;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+
+/**
+ * Dummy shell which prints a message and terminates.
+ * <p>
+ * This implementation is used to ensure clients who try to SSH directly to this
+ * server without supplying a command will get a reasonable error message, but
+ * cannot continue further.
+ */
+class NoShell implements ShellFactory {
+  public Shell createShell() {
+    return new Shell() {
+      private InputStream in;
+      private OutputStream out;
+      private OutputStream err;
+      private ExitCallback exit;
+
+      public void setInputStream(final InputStream in) {
+        this.in = in;
+      }
+
+      public void setOutputStream(final OutputStream out) {
+        this.out = out;
+      }
+
+      public void setErrorStream(final OutputStream err) {
+        this.err = err;
+      }
+
+      public void setExitCallback(final ExitCallback callback) {
+        this.exit = callback;
+      }
+
+      public void start(final Environment env) throws IOException {
+        err.write(Constants.encodeASCII("gerrit: no shell available\n"));
+        in.close();
+        out.close();
+        err.close();
+        exit.onExit(127);
+      }
+
+      public void destroy() {
+      }
+    };
+  }
+}