Describe HEAD if no explicit target was set

Change-Id: I5a5a238709df813ec07278bb3b4f9ea5c85c0883
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/api/DescribeCommandTest.java

@@ -42,16 +42,19 @@
  */
 package org.eclipse.jgit.api;
 
-import org.eclipse.jgit.api.errors.GitAPIException;
-import org.eclipse.jgit.junit.RepositoryTestCase;
-import org.eclipse.jgit.lib.ObjectId;
-import org.junit.Test;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
 
 import java.io.File;
 import java.io.FileWriter;
 import java.io.IOException;
 
-import static org.junit.Assert.*;
+import org.eclipse.jgit.api.errors.GitAPIException;
+import org.eclipse.jgit.api.errors.RefNotFoundException;
+import org.eclipse.jgit.junit.RepositoryTestCase;
+import org.eclipse.jgit.lib.ObjectId;
+import org.junit.Test;
 
 public class DescribeCommandTest extends RepositoryTestCase {
 
@@ -63,7 +66,7 @@ public class DescribeCommandTest extends RepositoryTestCase {
 		git = new Git(db);
 	}
 
-	@Test(expected = IllegalArgumentException.class)
+	@Test(expected = RefNotFoundException.class)
 	public void noTargetSet() throws Exception {
 		git.describe().call();
 	}
@@ -87,6 +90,9 @@ public class DescribeCommandTest extends RepositoryTestCase {
 		assertNameStartsWith(c4, "3e563c5");
 		// the value verified with git-describe(1)
 		assertEquals("t2-1-g3e563c5", describe(c4));
+
+		// test default target
+		assertEquals("t2-1-g3e563c5", git.describe().call());
 	}
 
 	/**

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

@@ -478,7 +478,6 @@ systemConfigFileInvalid=Systen wide config file {0} is invalid {1}
 tagAlreadyExists=tag ''{0}'' already exists
 tagNameInvalid=tag name {0} is invalid
 tagOnRepoWithoutHEADCurrentlyNotSupported=Tag on repository without HEAD currently not supported
-targetIsNotSet=Target is not set
 theFactoryMustNotBeNull=The factory must not be null
 timerAlreadyTerminated=Timer already terminated
 topologicalSortRequired=Topological sort required.

org.eclipse.jgit/src/org/eclipse/jgit/api/DescribeCommand.java

@@ -48,6 +48,7 @@ import org.eclipse.jgit.api.errors.RefNotFoundException;
 import org.eclipse.jgit.errors.IncorrectObjectTypeException;
 import org.eclipse.jgit.errors.MissingObjectException;
 import org.eclipse.jgit.internal.JGitText;
+import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.lib.Repository;
@@ -135,14 +136,16 @@ public class DescribeCommand extends GitCommand<String> {
 	}
 
 	/**
-	 * Describes the specified commit.
+	 * Describes the specified commit. Target defaults to HEAD if no commit was
+	 * set explicitly.
 	 *
-	 * @return if there's a tag that points to the commit being described, this tag name
-	 *         is returned. Otherwise additional suffix is added to the nearest tag, just
-	 *         like git-describe(1).
+	 * @return if there's a tag that points to the commit being described, this
+	 *         tag name is returned. Otherwise additional suffix is added to the
+	 *         nearest tag, just like git-describe(1).
 	 *         <p/>
-	 *         If none of the ancestors of the commit being described has any tags at all,
-	 *         then this method returns null, indicating that there's no way to describe this tag.
+	 *         If none of the ancestors of the commit being described has any
+	 *         tags at all, then this method returns null, indicating that
+	 *         there's no way to describe this tag.
 	 */
 	@Override
 	public String call() throws GitAPIException {
@@ -150,7 +153,7 @@ public class DescribeCommand extends GitCommand<String> {
 			checkCallable();
 
 			if (target == null)
-				throw new IllegalArgumentException(JGitText.get().targetIsNotSet);
+				setTarget(Constants.HEAD);
 
 			Map<ObjectId, Ref> tags = new HashMap<ObjectId, Ref>();
 

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

@@ -540,7 +540,6 @@ public class JGitText extends TranslationBundle {
 	/***/ public String tagAlreadyExists;
 	/***/ public String tagNameInvalid;
 	/***/ public String tagOnRepoWithoutHEADCurrentlyNotSupported;
-	/***/ public String targetIsNotSet;
 	/***/ public String theFactoryMustNotBeNull;
 	/***/ public String timerAlreadyTerminated;
 	/***/ public String topologicalSortRequired;