Don't raise checkout conflict for file missing in working tree

During a checkout we want to prevent to overwrite unsaved local file
content. Jgit was therefore checking whether the file to overwrite is
dirty or missing and would raise a conflict if this was the case. That
was wrong. It should only check if the file is dirty. It's ok to
"overwrite" a missing/non-existing file.

Change-Id: I63c3a94f663c87f09170fdf8b1b1bf4ed5246fc5
Signed-off-by: Christian Halstrick <christian.halstrick@sap.com>

org.eclipse.jgit.pgm.test/META-INF/MANIFEST.MF

@@ -18,6 +18,7 @@ Import-Package: org.eclipse.jgit.api;version="[3.3.0,3.4.0)",
  org.eclipse.jgit.revwalk;version="[3.3.0,3.4.0)",
  org.eclipse.jgit.storage.file;version="[3.3.0,3.4.0)",
  org.eclipse.jgit.transport;version="[3.3.0,3.4.0)",
+ org.eclipse.jgit.treewalk;version="[3.3.0,3.4.0)",
  org.eclipse.jgit.util;version="[3.3.0,3.4.0)",
  org.eclipse.jgit.util.io;version="[3.3.0,3.4.0)",
  org.hamcrest.core;bundle-version="[1.1.0,2.0.0)",

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

@@ -46,6 +46,10 @@ import java.io.File;
 
 import org.eclipse.jgit.api.Git;
 import org.eclipse.jgit.lib.CLIRepositoryTestCase;
+import org.eclipse.jgit.lib.FileMode;
+import org.eclipse.jgit.lib.Ref;
+import org.eclipse.jgit.treewalk.FileTreeIterator;
+import org.eclipse.jgit.treewalk.FileTreeIterator.FileEntry;
 import org.eclipse.jgit.util.FileUtils;
 import org.junit.Assert;
 import org.junit.Test;
@@ -133,6 +137,52 @@ public class CheckoutTest extends CLIRepositoryTestCase {
 		Assert.assertEquals("\ta", execute[1]);
 	}
 
+	/**
+	 * Steps:
+	 * <ol>
+	 * <li>Add file 'a' and 'b'
+	 * <li>Commit
+	 * <li>Create branch '1'
+	 * <li>modify file 'a'
+	 * <li>Commit
+	 * <li>Delete file 'a' in the working tree
+	 * <li>Checkout branch '1'
+	 * </ol>
+	 * The working tree should contain 'a' with FileMode.REGULAR_FILE after the
+	 * checkout.
+	 *
+	 * @throws Exception
+	 */
+	@Test
+	public void testCheckoutWithMissingWorkingTreeFile() throws Exception {
+		Git git = new Git(db);
+		File fileA = writeTrashFile("a", "Hello world a");
+		writeTrashFile("b", "Hello world b");
+		git.add().addFilepattern(".").call();
+		git.commit().setMessage("add files a & b").call();
+		Ref branch_1 = git.branchCreate().setName("branch_1").call();
+		writeTrashFile("a", "b");
+		git.add().addFilepattern("a").call();
+		git.commit().setMessage("modify file a").call();
+
+		FileEntry entry = new FileTreeIterator.FileEntry(new File(
+				db.getWorkTree(), "a"), db.getFS());
+		assertEquals(FileMode.REGULAR_FILE, entry.getMode());
+
+		FileUtils.delete(fileA);
+
+		git.checkout().setName(branch_1.getName()).call();
+
+		entry = new FileTreeIterator.FileEntry(new File(db.getWorkTree(), "a"),
+				db.getFS());
+		assertEquals(FileMode.REGULAR_FILE, entry.getMode());
+		assertEquals("Hello world a", read(fileA));
+	}
+
+	static private void assertEquals(Object expected, Object actual) {
+		Assert.assertEquals(expected, actual);
+	}
+
 	static private void assertEquals(String expected, String[] actual) {
 		// if there is more than one line, ignore last one if empty
 		Assert.assertEquals(

org.eclipse.jgit/src/org/eclipse/jgit/dircache/DirCacheCheckout.java

@@ -909,9 +909,9 @@ public class DirCacheCheckout {
 						// file content
 						update(name, mId, mMode);
 					} else if (dce != null
-							&& (f == null || f.isModified(dce, true,
+							&& (f != null && f.isModified(dce, true,
 									this.walk.getObjectReader()))) {
-						// File doesn't exist or is dirty
+						// File exists and is dirty
 						// Head and Index don't contain a submodule
 						// Head contains the same as Index. Merge differs
 						// Something in Merge
@@ -919,7 +919,7 @@ public class DirCacheCheckout {
 						// but the file is dirty. Report a conflict
 						conflict(name, dce, h, m);
 					} else {
-						// File exists and is clean
+						// File doesn't exist or is clean
 						// Head and Index don't contain a submodule
 						// Head contains the same as Index. Merge differs
 						// Something in Merge