Add -q option to suppress banner.

To minimize output when running tests.

Change-Id: Ia97c93cae31722d780ebf9714c6e508bb1630274

Documentation/pgm-prolog-shell.txt

@@ -7,7 +7,7 @@ prolog-shell - Simple interactive Prolog interpreter
 [verse]
 --
 _java_ -jar gerrit.war _prolog-shell_
-  [-s FILE.pl ...]
+  [-q] [-s FILE.pl ...]
 --
 
 == DESCRIPTION
@@ -15,6 +15,8 @@ Provides a simple interactive Prolog interpreter for development
 and testing.
 
 == OPTIONS
+-q::
+	Do not display banner.
 -s::
 	Dynamically load the Prolog source code at startup,
 	as though the user had entered `['FILE.pl'].` into

java/com/google/gerrit/pgm/PrologShell.java

@@ -30,9 +30,14 @@ public class PrologShell extends AbstractProgram {
   @Option(name = "-s", metaVar = "FILE.pl", usage = "file to load")
   private List<String> fileName = new ArrayList<>();
 
+  @Option(name = "-q", usage = "quiet mode without banner")
+  private boolean quiet;
+
   @Override
   public int run() {
-    banner();
+    if (!quiet) {
+      banner();
+    }
 
     BufferingPrologControl pcl = new BufferingPrologControl();
     pcl.setPrologClassLoader(new PrologClassLoader(getClass().getClassLoader()));
@@ -55,7 +60,9 @@ public class PrologShell extends AbstractProgram {
 
     try {
       pcl.execute(Prolog.BUILTIN, "cafeteria");
-      write("% halt\n");
+      if (!quiet) {
+        write("% halt\n");
+      }
       return 0;
     } catch (HaltException halt) {
       write("% halt(" + halt.getStatus() + ")\n");