Add git checkout --orphan implementation

Change-Id: I7bb583674641efed210d3cd5b86af27d7bb48e97
Signed-off-by: SATO taichi <ryushi@gmail.com>

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

@@ -59,7 +59,9 @@ import java.io.IOException;
 
 import org.eclipse.jgit.api.CheckoutResult.Status;
 import org.eclipse.jgit.api.errors.GitAPIException;
+import org.eclipse.jgit.api.errors.InvalidRefNameException;
 import org.eclipse.jgit.api.errors.JGitInternalException;
+import org.eclipse.jgit.api.errors.RefAlreadyExistsException;
 import org.eclipse.jgit.api.errors.RefNotFoundException;
 import org.eclipse.jgit.dircache.DirCache;
 import org.eclipse.jgit.dircache.DirCacheEntry;
@@ -351,4 +353,98 @@ public class CheckoutCommandTest extends RepositoryTestCase {
 		assertEquals(size, entry.getLength());
 		assertEquals(mTime, entry.getLastModified());
 	}
+
+	@Test
+	public void testCheckoutOrphanBranch() throws Exception {
+		CheckoutCommand co = newOrphanBranchCommand();
+		assertCheckoutRef(co.call());
+
+		File HEAD = new File(trash, ".git/HEAD");
+		String headRef = read(HEAD);
+		assertEquals("ref: refs/heads/orphanbranch\n", headRef);
+		assertEquals(2, trash.list().length);
+
+		File heads = new File(trash, ".git/refs/heads");
+		assertEquals(2, heads.listFiles().length);
+
+		this.assertNoHead();
+		this.assertRepositoryCondition(1);
+		assertEquals(CheckoutResult.NOT_TRIED_RESULT, co.getResult());
+	}
+
+	private CheckoutCommand newOrphanBranchCommand() {
+		return git.checkout().setOrphan(true)
+				.setName("orphanbranch");
+	}
+
+	private static void assertCheckoutRef(Ref ref) {
+		assertNotNull(ref);
+		assertEquals("refs/heads/orphanbranch", ref.getTarget().getName());
+	}
+
+	private void assertNoHead() throws IOException {
+		assertNull(db.resolve("HEAD"));
+	}
+
+	private void assertRepositoryCondition(int files) throws GitAPIException {
+		org.eclipse.jgit.api.Status status = this.git.status().call();
+		assertFalse(status.isClean());
+		assertEquals(files, status.getAdded().size());
+	}
+
+	@Test
+	public void testCreateOrphanBranchWithStartCommit() throws Exception {
+		CheckoutCommand co = newOrphanBranchCommand();
+		Ref ref = co.setStartPoint(initialCommit).call();
+		assertCheckoutRef(ref);
+		assertEquals(2, trash.list().length);
+		this.assertNoHead();
+		this.assertRepositoryCondition(1);
+	}
+
+	@Test
+	public void testCreateOrphanBranchWithStartPoint() throws Exception {
+		CheckoutCommand co = newOrphanBranchCommand();
+		Ref ref = co.setStartPoint("HEAD^").call();
+		assertCheckoutRef(ref);
+
+		assertEquals(2, trash.list().length);
+		this.assertNoHead();
+		this.assertRepositoryCondition(1);
+	}
+
+	@Test
+	public void testInvalidRefName() throws Exception {
+		try {
+			git.checkout().setOrphan(true).setName("../invalidname").call();
+			fail("Should have failed");
+		} catch (InvalidRefNameException e) {
+			// except to hit here
+		}
+	}
+
+	@Test
+	public void testNullRefName() throws Exception {
+		try {
+			git.checkout().setOrphan(true).setName(null).call();
+			fail("Should have failed");
+		} catch (InvalidRefNameException e) {
+			// except to hit here
+		}
+	}
+
+	@Test
+	public void testAlreadyExists() throws Exception {
+		this.git.checkout().setCreateBranch(true).setName("orphanbranch")
+				.call();
+		this.git.checkout().setName("master").call();
+
+		try {
+			newOrphanBranchCommand().call();
+			fail("Should have failed");
+		} catch (RefAlreadyExistsException e) {
+			// except to hit here
+		}
+	}
+
 }

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

@@ -47,6 +47,7 @@ import java.io.File;
 import java.io.IOException;
 import java.text.MessageFormat;
 import java.util.ArrayList;
+import java.util.EnumSet;
 import java.util.LinkedList;
 import java.util.List;
 
@@ -158,6 +159,8 @@ public class CheckoutCommand extends GitCommand<Ref> {
 
 	private boolean createBranch = false;
 
+	private boolean orphan = false;
+
 	private CreateBranchCommand.SetupUpstreamMode upstreamMode;
 
 	private String startPoint = null;
@@ -197,8 +200,8 @@ public class CheckoutCommand extends GitCommand<Ref> {
 			RefNotFoundException, InvalidRefNameException,
 			CheckoutConflictException {
 		checkCallable();
-		processOptions();
 		try {
+			processOptions();
 			if (checkoutAllPaths || !paths.isEmpty()) {
 				checkoutPaths();
 				status = new CheckoutResult(Status.OK, paths);
@@ -219,10 +222,25 @@ public class CheckoutCommand extends GitCommand<Ref> {
 			Ref headRef = repo.getRef(Constants.HEAD);
 			String shortHeadRef = getShortBranchName(headRef);
 			String refLogMessage = "checkout: moving from " + shortHeadRef; //$NON-NLS-1$
-			ObjectId branch = repo.resolve(name);
-			if (branch == null)
-				throw new RefNotFoundException(MessageFormat.format(JGitText
-						.get().refNotResolved, name));
+			ObjectId branch;
+			if (orphan) {
+				if (startPoint == null && startCommit == null) {
+					Result r = repo.updateRef(Constants.HEAD).link(
+							getBranchName());
+					if (!EnumSet.of(Result.NEW, Result.FORCED).contains(r))
+						throw new JGitInternalException(MessageFormat.format(
+								JGitText.get().checkoutUnexpectedResult,
+								r.name()));
+					this.status = CheckoutResult.NOT_TRIED_RESULT;
+					return repo.getRef(Constants.HEAD);
+				}
+				branch = getStartPoint();
+			} else {
+				branch = repo.resolve(name);
+				if (branch == null)
+					throw new RefNotFoundException(MessageFormat.format(
+							JGitText.get().refNotResolved, name));
+			}
 
 			RevWalk revWalk = new RevWalk(repo);
 			AnyObjectId headId = headRef.getObjectId();
@@ -256,7 +274,10 @@ public class CheckoutCommand extends GitCommand<Ref> {
 			Result updateResult;
 			if (ref != null)
 				updateResult = refUpdate.link(ref.getName());
-			else {
+			else if (orphan) {
+				updateResult = refUpdate.link(getBranchName());
+				ref = repo.getRef(Constants.HEAD);
+			} else {
 				refUpdate.setNewObjectId(newCommit);
 				updateResult = refUpdate.forceUpdate();
 			}
@@ -465,12 +486,27 @@ public class CheckoutCommand extends GitCommand<Ref> {
 		return result;
 	}
 
-	private void processOptions() throws InvalidRefNameException {
-		if ((!checkoutAllPaths && paths.isEmpty())
+	private void processOptions() throws InvalidRefNameException,
+			RefAlreadyExistsException, IOException {
+		if (((!checkoutAllPaths && paths.isEmpty()) || orphan)
 				&& (name == null || !Repository
 						.isValidRefName(Constants.R_HEADS + name)))
 			throw new InvalidRefNameException(MessageFormat.format(JGitText
 					.get().branchNameInvalid, name == null ? "<null>" : name)); //$NON-NLS-1$
+
+		if (orphan) {
+			Ref refToCheck = repo.getRef(getBranchName());
+			if (refToCheck != null)
+				throw new RefAlreadyExistsException(MessageFormat.format(
+						JGitText.get().refAlreadyExists, name));
+		}
+	}
+
+	private String getBranchName() {
+		if (name.startsWith(Constants.R_REFS))
+			return name;
+
+		return Constants.R_HEADS + name;
 	}
 
 	/**
@@ -516,6 +552,25 @@ public class CheckoutCommand extends GitCommand<Ref> {
 		return this;
 	}
 
+	/**
+	 * Specify whether to create a new orphan branch.
+	 * <p>
+	 * If <code>true</code> is used, the name of the new orphan branch must be
+	 * set using {@link #setName(String)}. The commit at which to start the new
+	 * orphan branch can be set using {@link #setStartPoint(String)} or
+	 * {@link #setStartPoint(RevCommit)}; if not specified, HEAD is used.
+	 *
+	 * @param orphan
+	 *            if <code>true</code> a orphan branch will be created as part
+	 *            of the checkout to the specified start point
+	 * @return this instance
+	 */
+	public CheckoutCommand setOrphan(boolean orphan) {
+		checkCallable();
+		this.orphan = orphan;
+		return this;
+	}
+
 	/**
 	 * Specify to force the ref update in case of a branch switch.
 	 *