Implemented merge for parallel delete/modification

Duplicates cgit behaviour for merging the case where
OURS is deleted and THEIRS is modified as well as
OURS is modified and THEIRS id deleted.

Change-Id: Ia2ab4f8dc95020f2914ff01c2bf3b1bc62a9d45d
Signed-off-by: Chris Aniszczyk <caniszczyk@gmail.com>

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

@@ -587,6 +587,69 @@ public class MergeCommandTest extends RepositoryTestCase {
 		assertEquals("1\nd\n3\n", read(new File(db.getWorkTree(), "d")));
 	}
 
+	@Test
+	public void testDeletionOnMasterConflict() throws Exception {
+		Git git = new Git(db);
+
+		writeTrashFile("a", "1\na\n3\n");
+		writeTrashFile("b", "1\nb\n3\n");
+		git.add().addFilepattern("a").addFilepattern("b").call();
+		RevCommit initialCommit = git.commit().setMessage("initial").call();
+
+		// create side branch and modify "a"
+		createBranch(initialCommit, "refs/heads/side");
+		checkoutBranch("refs/heads/side");
+		writeTrashFile("a", "1\na(side)\n3\n");
+		git.add().addFilepattern("a").call();
+		RevCommit secondCommit = git.commit().setMessage("side").call();
+
+		// delete a on master to generate conflict
+		checkoutBranch("refs/heads/master");
+		git.rm().addFilepattern("a").call();
+		git.commit().setMessage("main").call();
+
+		// merge side with master
+		MergeResult result = git.merge().include(secondCommit.getId())
+				.setStrategy(MergeStrategy.RESOLVE).call();
+		assertEquals(MergeStatus.CONFLICTING, result.getMergeStatus());
+
+		// result should be 'a' conflicting with workspace content from side
+		assertTrue(new File(db.getWorkTree(), "a").exists());
+		assertEquals("1\na(side)\n3\n", read(new File(db.getWorkTree(), "a")));
+		assertEquals("1\nb\n3\n", read(new File(db.getWorkTree(), "b")));
+	}
+
+	@Test
+	public void testDeletionOnSideConflict() throws Exception {
+		Git git = new Git(db);
+
+		writeTrashFile("a", "1\na\n3\n");
+		writeTrashFile("b", "1\nb\n3\n");
+		git.add().addFilepattern("a").addFilepattern("b").call();
+		RevCommit initialCommit = git.commit().setMessage("initial").call();
+
+		// create side branch and delete "a"
+		createBranch(initialCommit, "refs/heads/side");
+		checkoutBranch("refs/heads/side");
+		git.rm().addFilepattern("a").call();
+		RevCommit secondCommit = git.commit().setMessage("side").call();
+
+		// update a on master to generate conflict
+		checkoutBranch("refs/heads/master");
+		writeTrashFile("a", "1\na(main)\n3\n");
+		git.add().addFilepattern("a").call();
+		git.commit().setMessage("main").call();
+
+		// merge side with master
+		MergeResult result = git.merge().include(secondCommit.getId())
+				.setStrategy(MergeStrategy.RESOLVE).call();
+		assertEquals(MergeStatus.CONFLICTING, result.getMergeStatus());
+
+		assertTrue(new File(db.getWorkTree(), "a").exists());
+		assertEquals("1\na(main)\n3\n", read(new File(db.getWorkTree(), "a")));
+		assertEquals("1\nb\n3\n", read(new File(db.getWorkTree(), "b")));
+	}
+
 	@Test
 	public void testMergeFailingWithDirtyWorkingTree() throws Exception {
 		Git git = new Git(db);

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

@@ -138,7 +138,7 @@ public class DirCacheCheckoutTest extends ReadTreeTest {
 		assertEquals(MergeStatus.CONFLICTING, git.merge().include(master)
 				.call().getMergeStatus());
 		assertEquals(
-				"[E/h, mode:100644][G/i, mode:100644][f, mode:100644, stage:1][f, mode:100644, stage:2][f, mode:100644, stage:3]",
+				"[D/g, mode:100644, stage:1][D/g, mode:100644, stage:3][E/h, mode:100644][G/i, mode:100644][f, mode:100644, stage:1][f, mode:100644, stage:2][f, mode:100644, stage:3]",
 				indexState(0));
 
 		resetHard(master);

org.eclipse.jgit/src/org/eclipse/jgit/merge/ResolveMerger.java

@@ -452,6 +452,29 @@ public class ResolveMerger extends ThreeWayMerger {
 				unmergedPaths.add(tw.getPathString());
 			}
 			modifiedFiles.add(tw.getPathString());
+		} else if (modeO != modeT) {
+			// OURS or THEIRS has been deleted
+			if (((modeO != 0 && !tw.idEqual(T_BASE, T_OURS)) || (modeT != 0 && !tw
+					.idEqual(T_BASE, T_THEIRS)))) {
+
+				add(tw.getRawPath(), base, DirCacheEntry.STAGE_1);
+				add(tw.getRawPath(), ours, DirCacheEntry.STAGE_2);
+				DirCacheEntry e = add(tw.getRawPath(), theirs,
+						DirCacheEntry.STAGE_3);
+
+				// OURS was deleted checkout THEIRS
+				if (modeO == 0) {
+					// Check worktree before checking out THEIRS
+					if (isWorktreeDirty())
+						return false;
+					if (nonTree(modeT)) {
+						if (e != null)
+							toBeCheckedOut.put(tw.getPathString(), e);
+					}
+				}
+
+				unmergedPaths.add(tw.getPathString());
+			}
 		}
 		return true;
 	}