Checkout should be able to override modified symbolic links

Handle existing symlink as a file, not as directory if deleting a file
before creating (overriding) a symlink.

Bug: 484491
Change-Id: I29dbf57d1daec2ba98454975b093e1d381d05196
Signed-off-by: Andrey Loskutov <loskutov@gmx.de>

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

@@ -43,10 +43,12 @@
 package org.eclipse.jgit.api;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 
 import java.io.File;
 import java.io.IOException;
+import java.nio.file.Path;
 
 import org.eclipse.jgit.api.CheckoutCommand.Stage;
 import org.eclipse.jgit.api.errors.JGitInternalException;
@@ -59,6 +61,9 @@ import org.eclipse.jgit.lib.ObjectReader;
 import org.eclipse.jgit.lib.RepositoryState;
 import org.eclipse.jgit.lib.StoredConfig;
 import org.eclipse.jgit.revwalk.RevCommit;
+import org.eclipse.jgit.util.FS;
+import org.eclipse.jgit.util.FileUtils;
+import org.junit.Assume;
 import org.junit.Before;
 import org.junit.Test;
 
@@ -73,6 +78,8 @@ public class PathCheckoutCommandTest extends RepositoryTestCase {
 
 	private static final String FILE3 = "Test3.txt";
 
+	private static final String LINK = "link";
+
 	Git git;
 
 	RevCommit initialCommit;
@@ -98,6 +105,64 @@ public class PathCheckoutCommandTest extends RepositoryTestCase {
 		git.commit().setMessage("Third commit").call();
 	}
 
+	@Test
+	public void testUpdateSymLink() throws Exception {
+		Assume.assumeTrue(FS.DETECTED.supportsSymlinks());
+
+		Path path = writeLink(LINK, FILE1);
+		git.add().addFilepattern(LINK).call();
+		git.commit().setMessage("Added link").call();
+		assertEquals("3", read(path.toFile()));
+
+		writeLink(LINK, FILE2);
+		assertEquals("c", read(path.toFile()));
+
+		CheckoutCommand co = git.checkout();
+		co.addPath(LINK).call();
+
+		assertEquals("3", read(path.toFile()));
+	}
+
+	@Test
+	public void testUpdateBrokenSymLinkToDirectory() throws Exception {
+		Assume.assumeTrue(FS.DETECTED.supportsSymlinks());
+
+		Path path = writeLink(LINK, "f");
+		git.add().addFilepattern(LINK).call();
+		git.commit().setMessage("Added link").call();
+		assertEquals("f", FileUtils.readSymLink(path.toFile()));
+		assertTrue(path.toFile().exists());
+
+		writeLink(LINK, "link_to_nowhere");
+		assertFalse(path.toFile().exists());
+		assertEquals("link_to_nowhere", FileUtils.readSymLink(path.toFile()));
+
+		CheckoutCommand co = git.checkout();
+		co.addPath(LINK).call();
+
+		assertEquals("f", FileUtils.readSymLink(path.toFile()));
+	}
+
+	@Test
+	public void testUpdateBrokenSymLink() throws Exception {
+		Assume.assumeTrue(FS.DETECTED.supportsSymlinks());
+
+		Path path = writeLink(LINK, FILE1);
+		git.add().addFilepattern(LINK).call();
+		git.commit().setMessage("Added link").call();
+		assertEquals("3", read(path.toFile()));
+		assertEquals(FILE1, FileUtils.readSymLink(path.toFile()));
+
+		writeLink(LINK, "link_to_nowhere");
+		assertFalse(path.toFile().exists());
+		assertEquals("link_to_nowhere", FileUtils.readSymLink(path.toFile()));
+
+		CheckoutCommand co = git.checkout();
+		co.addPath(LINK).call();
+
+		assertEquals("3", read(path.toFile()));
+	}
+
 	@Test
 	public void testUpdateWorkingDirectory() throws Exception {
 		CheckoutCommand co = git.checkout();

org.eclipse.jgit.test/tst/org/eclipse/jgit/util/FileUtilTest.java

@@ -54,6 +54,7 @@ import java.util.regex.Matcher;
 
 import org.eclipse.jgit.junit.JGitTestUtil;
 import org.junit.After;
+import org.junit.Assume;
 import org.junit.Before;
 import org.junit.Test;
 
@@ -424,18 +425,27 @@ public class FileUtilTest {
 	@Test
 	public void testCreateSymlink() throws IOException {
 		FS fs = FS.DETECTED;
-		try {
-			fs.createSymLink(new File(trash, "x"), "y");
-		} catch (IOException e) {
-			if (fs.supportsSymlinks())
-				fail("FS claims to support symlinks but attempt to create symlink failed");
-			return;
-		}
-		assertTrue(fs.supportsSymlinks());
+		// show test as ignored if the FS doesn't support symlinks
+		Assume.assumeTrue(fs.supportsSymlinks());
+		fs.createSymLink(new File(trash, "x"), "y");
 		String target = fs.readSymLink(new File(trash, "x"));
 		assertEquals("y", target);
 	}
 
+	@Test
+	public void testCreateSymlinkOverrideExisting() throws IOException {
+		FS fs = FS.DETECTED;
+		// show test as ignored if the FS doesn't support symlinks
+		Assume.assumeTrue(fs.supportsSymlinks());
+		File file = new File(trash, "x");
+		fs.createSymLink(file, "y");
+		String target = fs.readSymLink(file);
+		assertEquals("y", target);
+		fs.createSymLink(file, "z");
+		target = fs.readSymLink(file);
+		assertEquals("z", target);
+	}
+
 	@Test
 	public void testRelativize_doc() {
 		// This is the javadoc example

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

@@ -409,7 +409,9 @@ public class FileUtils {
 			throws IOException {
 		Path nioPath = path.toPath();
 		if (Files.exists(nioPath, LinkOption.NOFOLLOW_LINKS)) {
-			if (Files.isRegularFile(nioPath)) {
+			BasicFileAttributes attrs = Files.readAttributes(nioPath,
+					BasicFileAttributes.class, LinkOption.NOFOLLOW_LINKS);
+			if (attrs.isRegularFile() || attrs.isSymbolicLink()) {
 				delete(path);
 			} else {
 				delete(path, EMPTY_DIRECTORIES_ONLY | RECURSIVE);