[spotbugs] Silence NP_BOOLEAN_RETURN_NULL in FakeUserAuthGSS#doAuth

Also mark the return value @Nullable to enable null analysis in Eclipse.

Change-Id: Ib954b231d743da6ea122adb2cc4880b5f99824cc
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit.junit.ssh/.settings/edu.umd.cs.findbugs.core.prefs

@@ -0,0 +1,145 @@
+#SpotBugs User Preferences
+#Fri Dec 04 11:26:04 CET 2020
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org.eclipse.jgit.junit.ssh/findBugs/FindBugsExcludeFilter.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<FindBugsFilter>
+     <!-- Silence returning null for Boolean return type -->
+     <Match>
+       <Class name="org.eclipse.jgit.junit.ssh.SshTestGitServer$FakeUserAuthGSS" />
+       <Method name="doAuth" />
+       <Bug pattern="NP_BOOLEAN_RETURN_NULL" />
+     </Match>
+</FindBugsFilter>

org.eclipse.jgit.junit.ssh/src/org/eclipse/jgit/junit/ssh/SshTestGitServer.java

@@ -54,6 +54,7 @@ import org.apache.sshd.server.shell.UnknownCommand;
 import org.apache.sshd.server.subsystem.SubsystemFactory;
 import org.apache.sshd.server.subsystem.sftp.SftpSubsystemFactory;
 import org.eclipse.jgit.annotations.NonNull;
+import org.eclipse.jgit.annotations.Nullable;
 import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.transport.ReceivePack;
 import org.eclipse.jgit.transport.RemoteConfig;
@@ -202,7 +203,7 @@ public class SshTestGitServer {
 
 	private static class FakeUserAuthGSS extends UserAuthGSS {
 		@Override
-		protected Boolean doAuth(Buffer buffer, boolean initial)
+		protected @Nullable Boolean doAuth(Buffer buffer, boolean initial)
 				throws Exception {
 			// We always reply that we did do this, but then we fail at the
 			// first token message. That way we can test that the client-side