branch command: print help if requested, even if arguments are wrong

git branch -d -h reports an error (because of missing -d option value)
but does not print the help as expected.

To fix this, CmdLineParser must catch, print but do not propagate
exceptions if help is requested.

Bug: 484951
Change-Id: I51265ebe295f22da540792c6a1980b8bdb295a02
Signed-off-by: Andrey Loskutov <loskutov@gmx.de>

org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/BranchTest.java

@@ -53,6 +53,7 @@
 import org.eclipse.jgit.lib.CLIRepositoryTestCase;
 import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.RefUpdate;
+import org.eclipse.jgit.pgm.internal.CLIText;
 import org.eclipse.jgit.revwalk.RevCommit;
 import org.junit.Before;
 import org.junit.Test;
@@ -65,6 +66,15 @@ public void setUp() throws Exception {
 		new Git(db).commit().setMessage("initial commit").call();
 	}
 
+	@Test
+	public void testHelpAfterDelete() throws Exception {
+		String err = toString(executeUnchecked("git branch -d"));
+		String help = toString(executeUnchecked("git branch -h"));
+		String errAndHelp = toString(executeUnchecked("git branch -d -h"));
+		assertEquals(CLIText.fatalError(CLIText.get().branchNameRequired), err);
+		assertEquals(toString(err, help), errAndHelp);
+	}
+
 	@Test
 	public void testList() throws Exception {
 		assertEquals("* master", toString(execute("git branch")));

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

@@ -277,8 +277,16 @@ protected void printUsage(final String message, final CmdLineParser clp)
 	}
 
 	/**
-	 * @return the resource bundle that will be passed to args4j for purpose
-	 *         of string localization
+	 * @return error writer, typically this is standard error.
+	 * @since 4.2
+	 */
+	public ThrowingPrintWriter getErrorWriter() {
+		return errw;
+	}
+
+	/**
+	 * @return the resource bundle that will be passed to args4j for purpose of
+	 *         string localization
 	 */
 	protected ResourceBundle getResourceBundle() {
 		return CLIText.get().resourceBundle();

org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/opt/CmdLineParser.java

@@ -43,6 +43,7 @@
 
 package org.eclipse.jgit.pgm.opt;
 
+import java.io.IOException;
 import java.io.Writer;
 import java.lang.reflect.Field;
 import java.util.ArrayList;
@@ -53,6 +54,7 @@
 
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.Repository;
+import org.eclipse.jgit.pgm.Die;
 import org.eclipse.jgit.pgm.TextBuiltin;
 import org.eclipse.jgit.pgm.internal.CLIText;
 import org.eclipse.jgit.revwalk.RevCommit;
@@ -95,6 +97,8 @@ public class CmdLineParser extends org.kohsuke.args4j.CmdLineParser {
 
 	private boolean seenHelp;
 
+	private TextBuiltin cmd;
+
 	/**
 	 * Creates a new command line owner that parses arguments/options and set
 	 * them into the given object.
@@ -126,8 +130,12 @@ public CmdLineParser(final Object bean) {
 	 */
 	public CmdLineParser(final Object bean, Repository repo) {
 		super(bean);
-		if (repo == null && bean instanceof TextBuiltin)
-			repo = ((TextBuiltin) bean).getRepository();
+		if (bean instanceof TextBuiltin) {
+			cmd = (TextBuiltin) bean;
+		}
+		if (repo == null && cmd != null) {
+			repo = cmd.getRepository();
+		}
 		this.db = repo;
 	}
 
@@ -167,6 +175,11 @@ public void parseArgument(final String... args) throws CmdLineException {
 
 		try {
 			super.parseArgument(tmp.toArray(new String[tmp.size()]));
+		} catch (Die e) {
+			if (!seenHelp) {
+				throw e;
+			}
+			printToErrorWriter(CLIText.fatalError(e.getMessage()));
 		} finally {
 			// reset "required" options to defaults for correct command printout
 			if (backup != null && !backup.isEmpty()) {
@@ -176,6 +189,18 @@ public void parseArgument(final String... args) throws CmdLineException {
 		}
 	}
 
+	private void printToErrorWriter(String error) {
+		if (cmd == null) {
+			System.err.println(error);
+		} else {
+			try {
+				cmd.getErrorWriter().println(error);
+			} catch (IOException e1) {
+				System.err.println(error);
+			}
+		}
+	}
+
 	private List<OptionHandler> unsetRequiredOptions() {
 		List<OptionHandler> options = getOptions();
 		List<OptionHandler> backup = new ArrayList<>(options);