Perform very detailed logging on unpack failures

If we catch an UnpackException it might be caused by a bug deep
within the check connectivity code of ReceivePack.  Log a lot more
detail than we have in the past to try and narrow down the problem.

Change-Id: I28b2e9e3183359eea6d0f33cb16ffc579f8a837e
Signed-off-by: Shawn O. Pearce <sop@google.com>

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

@@ -18,15 +18,22 @@ import com.google.gerrit.reviewdb.Account;
 import com.google.gerrit.server.IdentifiedUser;
 import com.google.gerrit.server.git.ReceiveCommits;
 import com.google.gerrit.server.git.TransferConfig;
+import com.google.gerrit.server.git.VisibleRefFilter;
 import com.google.gerrit.sshd.AbstractGitCommand;
 import com.google.inject.Inject;
 
+import org.eclipse.jgit.errors.UnpackException;
+import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.transport.ReceivePack;
+import org.eclipse.jgit.transport.RefFilter;
 import org.kohsuke.args4j.Option;
 
 import java.io.IOException;
 import java.io.InterruptedIOException;
+import java.util.ArrayList;
 import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
 import java.util.Set;
 
 /** Receives change upload over SSH using the Git receive-pack protocol. */
@@ -82,6 +89,49 @@ final class Receive extends AbstractGitCommand {
       rp.receive(in, out, err);
     } catch (InterruptedIOException err) {
       throw new Failure(128, "fatal: client IO read/write timeout", err);
+
+    } catch (UnpackException badStream) {
+      // This may have been triggered by branch level access controls.
+      // Log what the heck is going on, as detailed as we can.
+      //
+      StringBuilder msg = new StringBuilder();
+      msg.append("Unpack error on project \""
+          + projectControl.getProject().getName() + "\":\n");
+
+      msg.append("  RefFilter: " + rp.getRefFilter());
+      if (rp.getRefFilter() == RefFilter.DEFAULT) {
+        msg.append("DEFAULT");
+      } else if (rp.getRefFilter() instanceof VisibleRefFilter) {
+        msg.append("VisibleRefFilter");
+      } else {
+        msg.append(rp.getRefFilter().getClass());
+      }
+      msg.append("\n");
+
+      if (rp.getRefFilter() instanceof VisibleRefFilter) {
+        Map<String, Ref> adv = rp.getAdvertisedRefs();
+        msg.append("  Visible references (" + adv.size() + "):\n");
+        for (Ref ref : adv.values()) {
+          msg.append("  - " + ref.getObjectId().abbreviate(8).name() + " "
+              + ref.getName() + "\n");
+        }
+
+        List<Ref> hidden = new ArrayList<Ref>();
+        for (Ref ref : rp.getRepository().getAllRefs().values()) {
+          if (!adv.containsKey(ref.getName())) {
+            hidden.add(ref);
+          }
+        }
+
+        msg.append("  Hidden references (" + hidden.size() + "):\n");
+        for (Ref ref : hidden) {
+          msg.append("  - " + ref.getObjectId().abbreviate(8).name() + " "
+              + ref.getName() + "\n");
+        }
+      }
+
+      IOException detail = new IOException(msg.toString(), badStream);
+      throw new Failure(128, "fatal: Unpack error, check server log", detail);
     }
   }