Add IndexDiff tests for merge conflict state BOTH_ADDED

JGit handled this case improperly which these tests demonstrate. Fixed
by I25915880f304090fe90584c79bddf021231227a2.

Bug: 440537
Change-Id: Ia29c1d6cf8c0ce724cc3ff5ed9e0b396949b44bf
Signed-off-by: Laurent Goubet <laurent.goubet@obeo.fr>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/IndexDiffTest.java

@@ -578,6 +578,122 @@ public class IndexDiffTest extends RepositoryTestCase {
 		assertTrue(StageState.BOTH_ADDED.hasTheirs());
 	}
 
+	@Test
+	public void testStageState_mergeAndReset_bug() throws Exception {
+		Git git = new Git(db);
+
+		writeTrashFile("a", "content");
+		git.add().addFilepattern("a").call();
+		RevCommit initialCommit = git.commit().setMessage("initial commit")
+				.call();
+
+		// create branch and add a new file
+		final String branchName = Constants.R_HEADS + "branch";
+		createBranch(initialCommit, branchName);
+		checkoutBranch(branchName);
+		writeTrashFile("b", "second file content - branch");
+		git.add().addFilepattern("b").call();
+		RevCommit branchCommit = git.commit().setMessage("branch commit")
+				.call();
+
+		// checkout master and add the same new file
+		checkoutBranch(Constants.R_HEADS + Constants.MASTER);
+		writeTrashFile("b", "second file content - master");
+		git.add().addFilepattern("b").call();
+		git.commit().setMessage("master commit").call();
+
+		// try and merge
+		MergeResult result = git.merge().include(branchCommit).call();
+		assertEquals(MergeStatus.CONFLICTING, result.getMergeStatus());
+
+		FileTreeIterator iterator = new FileTreeIterator(db);
+		IndexDiff diff = new IndexDiff(db, Constants.HEAD, iterator);
+		diff.diff();
+
+		assertTrue(diff.getChanged().isEmpty());
+		assertTrue(diff.getAdded().isEmpty());
+		assertTrue(diff.getRemoved().isEmpty());
+		assertTrue(diff.getMissing().isEmpty());
+		assertTrue(diff.getModified().isEmpty());
+		assertEquals(1, diff.getConflicting().size());
+		assertTrue(diff.getConflicting().contains("b"));
+		assertEquals(StageState.BOTH_ADDED, diff.getConflictingStageStates()
+				.get("b"));
+		assertTrue(diff.getUntrackedFolders().isEmpty());
+
+		// reset file b to its master state without altering the index
+		writeTrashFile("b", "second file content - master");
+
+		// we should have the same result
+		iterator = new FileTreeIterator(db);
+		diff = new IndexDiff(db, Constants.HEAD, iterator);
+		diff.diff();
+
+		assertTrue(diff.getChanged().isEmpty());
+		assertTrue(diff.getAdded().isEmpty());
+		assertTrue(diff.getRemoved().isEmpty());
+		assertTrue(diff.getMissing().isEmpty());
+		assertTrue(diff.getModified().isEmpty());
+		assertEquals(1, diff.getConflicting().size());
+		assertTrue(diff.getConflicting().contains("b"));
+		assertEquals(StageState.BOTH_ADDED, diff.getConflictingStageStates()
+				.get("b"));
+		assertTrue(diff.getUntrackedFolders().isEmpty());
+	}
+
+	@Test
+	public void testStageState_simulated_bug() throws Exception {
+		Git git = new Git(db);
+
+		writeTrashFile("a", "content");
+		git.add().addFilepattern("a").call();
+		RevCommit initialCommit = git.commit().setMessage("initial commit")
+				.call();
+
+		// create branch and add a new file
+		final String branchName = Constants.R_HEADS + "branch";
+		createBranch(initialCommit, branchName);
+		checkoutBranch(branchName);
+		writeTrashFile("b", "second file content - branch");
+		git.add().addFilepattern("b").call();
+		git.commit().setMessage("branch commit")
+				.call();
+
+		// checkout master and add the same new file
+		checkoutBranch(Constants.R_HEADS + Constants.MASTER);
+		writeTrashFile("b", "second file content - master");
+		git.add().addFilepattern("b").call();
+		git.commit().setMessage("master commit").call();
+
+		// Simulate a failed merge of branch into master
+		DirCacheBuilder builder = db.lockDirCache().builder();
+		DirCacheEntry entry = createEntry("a", FileMode.REGULAR_FILE, 0,
+				"content");
+		builder.add(entry);
+		entry = createEntry("b", FileMode.REGULAR_FILE, 2,
+				"second file content - master");
+		builder.add(entry);
+		entry = createEntry("b", FileMode.REGULAR_FILE, 3,
+				"second file content - branch");
+		builder.add(entry);
+		builder.commit();
+
+		FileTreeIterator iterator = new FileTreeIterator(db);
+		IndexDiff diff = new IndexDiff(db, Constants.HEAD, iterator);
+		diff.diff();
+
+		assertTrue(diff.getChanged().isEmpty());
+		assertTrue(diff.getAdded().isEmpty());
+		assertTrue(diff.getRemoved().isEmpty());
+		assertTrue(diff.getMissing().isEmpty());
+		assertTrue(diff.getModified().isEmpty());
+		assertEquals(1, diff.getConflicting().size());
+		assertTrue(diff.getConflicting().contains("b"));
+		assertEquals(StageState.BOTH_ADDED, diff.getConflictingStageStates()
+				.get("b"));
+		assertTrue(diff.getUntrackedFolders().isEmpty());
+	}
+
 	@Test
 	public void testAutoCRLFInput() throws Exception {
 		Git git = new Git(db);