Write upload-pack metrics to sshd log

In order to enable detailed performance and problem analysis add
upload-pack metrics to the sshd log. The log format for upload-pack log
records is now enhanced to:
- timestamp
- session id
- thread name
- user name
- account id
- message
- command wait time
- command execution time
- time negotiating
- time searching for reuse
- time searching for sizes
- time counting
- time compressing
- time writing
- total time in UploadPack
- bitmap index misses (-1 means no bitmap index available)
- total deltas
- total objects
- total bytes transferred
- client agent

If statistics aren't available e.g. since an exception occurred they are
logged as -1.

Change-Id: I4ec08579cedfeb6a30eb41d2e2a110f4f8eee8fa

java/com/google/gerrit/sshd/SshLog.java

@@ -53,6 +53,7 @@ class SshLog implements LifecycleListener, GerritConfigListener {
   private static final String P_EXEC = "executionTime";
   private static final String P_STATUS = "status";
   private static final String P_AGENT = "agent";
+  private static final String P_MESSAGE = "message";
 
   private final Provider<SshSession> session;
   private final Provider<Context> context;
@@ -147,6 +148,10 @@ class SshLog implements LifecycleListener, GerritConfigListener {
   }
 
   void onExecute(DispatchCommand dcmd, int exitValue, SshSession sshSession) {
+    onExecute(dcmd, exitValue, sshSession, null);
+  }
+
+  void onExecute(DispatchCommand dcmd, int exitValue, SshSession sshSession, String message) {
     final Context ctx = context.get();
     ctx.finished = TimeUtil.nowMs();
 
@@ -180,6 +185,10 @@ class SshLog implements LifecycleListener, GerritConfigListener {
       event.setProperty(P_AGENT, peerAgent);
     }
 
+    if (message != null) {
+      event.setProperty(P_MESSAGE, message);
+    }
+
     if (async != null) {
       async.append(event);
     }