Use a dedicated executor to run auto-gc in command line interface

WorkQueue uses daemon threads so auto-gc would not be executed after
short-lived commands run in command line. Hence use a dedicated executor
which we shutdown when the command finishes.

Change-Id: I0c2429ecfa04387389d159168ba78a020a696228
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/Main.java

@@ -57,6 +57,10 @@ import java.text.MessageFormat;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Locale;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ThreadFactory;
+import java.util.concurrent.TimeUnit;
 
 import org.eclipse.jgit.awtui.AwtAuthenticator;
 import org.eclipse.jgit.awtui.AwtCredentialsProvider;
@@ -98,6 +102,8 @@ public class Main {
 
 	PrintWriter writer;
 
+	private ExecutorService gcExecutor;
+
 	/**
 	 *
 	 */
@@ -105,6 +111,17 @@ public class Main {
 		HttpTransport.setConnectionFactory(new HttpClientConnectionFactory());
 		CleanFilter.register();
 		SmudgeFilter.register();
+		gcExecutor = Executors.newSingleThreadExecutor(new ThreadFactory() {
+			private final ThreadFactory baseFactory = Executors
+					.defaultThreadFactory();
+
+			@Override
+			public Thread newThread(Runnable taskBody) {
+				Thread thr = baseFactory.newThread(taskBody);
+				thr.setName("JGit-autoGc"); //$NON-NLS-1$
+				return thr;
+			}
+		});
 	}
 
 	/**
@@ -192,6 +209,8 @@ public class Main {
 			// broken pipe
 			exit(1, null);
 		}
+		gcExecutor.shutdown();
+		gcExecutor.awaitTermination(10, TimeUnit.MINUTES);
 	}
 
 	PrintWriter createErrorWriter() {