FS: Extract GobblerThread into a private static class

The primary goal is to improve exception readability. Since this is a
standalone thread, just logging the stack trace of the caught
exception is not very useful:

java.io.IOException: Stream closed
	at java.io.BufferedInputStream.getBufIfOpen(BufferedInputStream.java:162)
	at java.io.BufferedInputStream.read(BufferedInputStream.java:258)
	at org.eclipse.jgit.util.FS$2.run(FS.java:451)

Providing a named class eliminates the "FS$2", and including the
command name provides a little more context in the error message.
A future improvement might include the stack trace that created the
GobblerThread as well.

Change-Id: Ibf16d15b47a85b6f41844a177e398c2fc94f27b0

org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties

@@ -257,6 +257,7 @@ exceptionCaughtDuringExecutionOfResetCommand=Exception caught during execution o
 exceptionCaughtDuringExecutionOfRevertCommand=Exception caught during execution of revert command. {0}
 exceptionCaughtDuringExecutionOfRmCommand=Exception caught during execution of rm command
 exceptionCaughtDuringExecutionOfTagCommand=Exception caught during execution of tag command
+exceptionCaughtDuringExcecutionOfCommand=Exception caught during execution of command {0} in {1}
 exceptionHookExecutionInterrupted=Execution of "{0}" hook interrupted.
 exceptionOccurredDuringAddingOfOptionToALogCommand=Exception occurred during adding of {0} as option to a Log command
 exceptionOccurredDuringReadingOfGIT_DIR=Exception occurred during reading of $GIT_DIR/{0}. {1}

org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java

@@ -316,6 +316,7 @@ public class JGitText extends TranslationBundle {
 	/***/ public String exceptionCaughtDuringExecutionOfRevertCommand;
 	/***/ public String exceptionCaughtDuringExecutionOfRmCommand;
 	/***/ public String exceptionCaughtDuringExecutionOfTagCommand;
+	/***/ public String exceptionCaughtDuringExcecutionOfCommand;
 	/***/ public String exceptionHookExecutionInterrupted;
 	/***/ public String exceptionOccurredDuringAddingOfOptionToALogCommand;
 	/***/ public String exceptionOccurredDuringReadingOfGIT_DIR;

org.eclipse.jgit/src/org/eclipse/jgit/util/FS.java

@@ -440,40 +440,11 @@ public abstract class FS {
 			if (env != null) {
 				pb.environment().putAll(env);
 			}
-			final Process p = pb.start();
-			final BufferedReader lineRead = new BufferedReader(
+			Process p = pb.start();
+			BufferedReader lineRead = new BufferedReader(
 					new InputStreamReader(p.getInputStream(), encoding));
 			p.getOutputStream().close();
-			final AtomicBoolean gooblerFail = new AtomicBoolean(false);
-			Thread gobbler = new Thread() {
-				public void run() {
-					InputStream is = p.getErrorStream();
-					try {
-						int ch;
-						if (debug)
-							while ((ch = is.read()) != -1)
-								System.err.print((char) ch);
-						else
-							while (is.read() != -1) {
-								// ignore
-							}
-					} catch (IOException e) {
-						// Just print on stderr for debugging
-						if (debug)
-							e.printStackTrace(System.err);
-						gooblerFail.set(true);
-					}
-					try {
-						is.close();
-					} catch (IOException e) {
-						// Just print on stderr for debugging
-						if (debug) {
-							LOG.debug("Caught exception in gobbler thread", e); //$NON-NLS-1$
-						}
-						gooblerFail.set(true);
-					}
-				}
-			};
+			GobblerThread gobbler = new GobblerThread(p, command, dir);
 			gobbler.start();
 			String r = null;
 			try {
@@ -498,7 +469,7 @@ public abstract class FS {
 					int rc = p.waitFor();
 					gobbler.join();
 					if (rc == 0 && r != null && r.length() > 0
-							&& !gooblerFail.get())
+							&& !gobbler.fail.get())
 						return r;
 					if (debug) {
 						LOG.debug("readpipe rc=" + rc); //$NON-NLS-1$
@@ -517,6 +488,59 @@ public abstract class FS {
 		return null;
 	}
 
+	private static class GobblerThread extends Thread {
+		private final Process p;
+		private final String desc;
+		private final String dir;
+		private final boolean debug = LOG.isDebugEnabled();
+		private final AtomicBoolean fail = new AtomicBoolean();
+
+		private GobblerThread(Process p, String[] command, File dir) {
+			this.p = p;
+			if (debug) {
+				this.desc = Arrays.asList(command).toString();
+				this.dir = dir.toString();
+			} else {
+				this.desc = null;
+				this.dir = null;
+			}
+		}
+
+		public void run() {
+			InputStream is = p.getErrorStream();
+			try {
+				int ch;
+				if (debug) {
+					while ((ch = is.read()) != -1) {
+						System.err.print((char) ch);
+					}
+				} else {
+					while (is.read() != -1) {
+						// ignore
+					}
+				}
+			} catch (IOException e) {
+				logError(e);
+				fail.set(true);
+			}
+			try {
+				is.close();
+			} catch (IOException e) {
+				logError(e);
+				fail.set(true);
+			}
+		}
+
+		private void logError(Throwable t) {
+			if (!debug) {
+				return;
+			}
+			String msg = MessageFormat.format(
+					JGitText.get().exceptionCaughtDuringExcecutionOfCommand, desc, dir);
+			LOG.debug(msg, t);
+		}
+	}
+
 	/**
 	 * @return the path to the Git executable or {@code null} if it cannot be
 	 *         determined.