Fix RecursiveMerger's internal use of merge to find a merge base

When RecursiveMerger tried to determine a common base tree it was
recursively tried to merge multiple common bases. But these intermediate
merges which have just been done to determine a single common base for
the final merge already filled some important fields (toBeCheckedOut,
toBeDeleted, ...). These side effects of the intermediate merges led to
wrong results of the final merge. One symptom was that after a recursive
merge which should be succesful you could still see leftover files in
the worktree: files which existed in the (virtual) common base but which
don't exist anymore in the branches to be merged.

The solution is easy: Clear the appropriate fields after common base
determination and start the final merge with a clean state.

Change-Id: I644ea9e1cb15360f7901bc0483cdb9286308c226
Signed-off-by: Robin Rosenberg <robin.rosenberg@dewire.com>

org.eclipse.jgit.junit/src/org/eclipse/jgit/junit/JGitTestUtil.java

@@ -229,6 +229,11 @@ public abstract class JGitTestUtil {
 		return read(file);
 	}
 
+	public static boolean check(final Repository db, final String name) {
+		File file = new File(db.getWorkTree(), name);
+		return file.exists();
+	}
+
 	public static void deleteTrashFile(final Repository db,
 			final String name) throws IOException {
 		File path = new File(db.getWorkTree(), name);

org.eclipse.jgit.junit/src/org/eclipse/jgit/junit/RepositoryTestCase.java

@@ -119,6 +119,10 @@ public abstract class RepositoryTestCase extends LocalDiskRepositoryTestCase {
 		return JGitTestUtil.read(db, name);
 	}
 
+	protected boolean check(final String name) {
+		return JGitTestUtil.check(db, name);
+	}
+
 	protected void deleteTrashFile(final String name) throws IOException {
 		JGitTestUtil.deleteTrashFile(db, name);
 	}

org.eclipse.jgit.test/tst/org/eclipse/jgit/merge/RecursiveMergerTest.java

@@ -44,6 +44,7 @@ package org.eclipse.jgit.merge;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
 
 import java.io.BufferedReader;
 import java.io.File;
@@ -178,7 +179,7 @@ public class RecursiveMergerTest extends RepositoryTestCase {
 	/**
 	 * Merging m2,s2 from the following topology. The same file is modified
 	 * in both branches. The modifications should be mergeable. m2 and s2
-	 * contain branch specific conflict resolutions. Therefore m2 and don't contain the same content.
+	 * contain branch specific conflict resolutions. Therefore m2 and s2 don't contain the same content.
 	 *
 	 * <pre>
 	 * m0--m1--m2
@@ -257,6 +258,183 @@ public class RecursiveMergerTest extends RepositoryTestCase {
 		}
 	}
 
+	@Theory
+	/**
+	 * Merging m2,s2 from the following topology. The same file is modified
+	 * in both branches. The modifications should be mergeable but only if the automerge of m1 and s1
+	 * is choosen as parent. Choosing m0 as parent would not be sufficient (in contrast to the merge in
+	 * crissCrossMerge_mergeable). m2 and s2 contain branch specific conflict resolutions. Therefore m2
+	 * and s2 don't contain the same content.
+	 *
+	 * <pre>
+	 * m0--m1--m2
+	 *   \   \/
+	 *    \  /\
+	 *     s1--s2
+	 * </pre>
+	 */
+	public void crissCrossMerge_mergeable2(MergeStrategy strategy,
+			IndexState indexState, WorktreeState worktreeState)
+			throws Exception {
+		if (!validateStates(indexState, worktreeState))
+			return;
+
+		BranchBuilder master = db_t.branch("master");
+		RevCommit m0 = master.commit().add("f", "1\n2\n3\n")
+				.message("m0")
+				.create();
+		RevCommit m1 = master.commit().add("f", "1-master\n2\n3\n")
+				.message("m1").create();
+		db_t.getRevWalk().parseCommit(m1);
+
+		BranchBuilder side = db_t.branch("side");
+		RevCommit s1 = side.commit().parent(m0).add("f", "1\n2\n3-side\n")
+				.message("s1").create();
+		RevCommit s2 = side.commit().parent(m1)
+				.add("f", "1-master\n2\n3-side-r\n")
+				.message("s2(merge)")
+				.create();
+		RevCommit m2 = master.commit().parent(s1)
+				.add("f", "1-master-r\n2\n3-side\n")
+				.message("m2(merge)")
+				.create();
+
+		Git git = Git.wrap(db);
+		git.checkout().setName("master").call();
+		modifyWorktree(worktreeState, "f", "side");
+		modifyIndex(indexState, "f", "side");
+
+		ResolveMerger merger = (ResolveMerger) strategy.newMerger(db,
+				worktreeState == WorktreeState.Bare);
+		if (worktreeState != WorktreeState.Bare)
+			merger.setWorkingTreeIterator(new FileTreeIterator(db));
+		try {
+			boolean expectSuccess = true;
+			if (!(indexState == IndexState.Bare
+					|| indexState == IndexState.Missing || indexState == IndexState.SameAsHead))
+				// index is dirty
+				expectSuccess = false;
+			else if (worktreeState == WorktreeState.DifferentFromHeadAndOther
+					|| worktreeState == WorktreeState.SameAsOther)
+				expectSuccess = false;
+			assertEquals(Boolean.valueOf(expectSuccess),
+					Boolean.valueOf(merger.merge(new RevCommit[] { m2, s2 })));
+			assertEquals(MergeStrategy.RECURSIVE, strategy);
+			if (!expectSuccess)
+				// if the merge was not successful skip testing the state of
+				// index and workingtree
+				return;
+			assertEquals(
+					"1-master-r\n2\n3-side-r",
+					contentAsString(db, merger.getResultTreeId(), "f"));
+			if (indexState != IndexState.Bare)
+				assertEquals(
+						"[f, mode:100644, content:1-master-r\n2\n3-side-r\n]",
+						indexState(RepositoryTestCase.CONTENT));
+			if (worktreeState != WorktreeState.Bare
+					&& worktreeState != WorktreeState.Missing)
+				assertEquals(
+						"1-master-r\n2\n3-side-r\n",
+						read("f"));
+		} catch (NoMergeBaseException e) {
+			assertEquals(MergeStrategy.RESOLVE, strategy);
+			assertEquals(e.getReason(),
+					MergeBaseFailureReason.MULTIPLE_MERGE_BASES_NOT_SUPPORTED);
+		}
+	}
+
+	@Theory
+	/**
+	 * Merging m2,s2 from the following topology. The same file is modified
+	 * in both branches. The modifications should be mergeable but only if the automerge of m1 and s1
+	 * is choosen as parent. On both branches delete and modify files untouched on the other branch.
+	 * On both branches create new files. Make sure these files are correctly merged and
+	 * exist in the workingtree.
+	 *
+	 * <pre>
+	 * m0--m1--m2
+	 *   \   \/
+	 *    \  /\
+	 *     s1--s2
+	 * </pre>
+	 */
+	public void crissCrossMerge_checkOtherFiles(MergeStrategy strategy,
+			IndexState indexState, WorktreeState worktreeState)
+			throws Exception {
+		if (!validateStates(indexState, worktreeState))
+			return;
+
+		BranchBuilder master = db_t.branch("master");
+		RevCommit m0 = master.commit().add("f", "1\n2\n3\n").add("m.m", "0")
+				.add("m.d", "0").add("s.m", "0").add("s.d", "0").message("m0")
+				.create();
+		RevCommit m1 = master.commit().add("f", "1-master\n2\n3\n")
+				.add("m.c", "0").add("m.m", "1").rm("m.d").message("m1")
+				.create();
+		db_t.getRevWalk().parseCommit(m1);
+
+		BranchBuilder side = db_t.branch("side");
+		RevCommit s1 = side.commit().parent(m0).add("f", "1\n2\n3-side\n")
+				.add("s.c", "0").add("s.m", "1").rm("s.d").message("s1")
+				.create();
+		RevCommit s2 = side.commit().parent(m1)
+				.add("f", "1-master\n2\n3-side-r\n").add("m.m", "1")
+				.add("m.c", "0").rm("m.d").message("s2(merge)").create();
+		RevCommit m2 = master.commit().parent(s1)
+				.add("f", "1-master-r\n2\n3-side\n").add("s.m", "1")
+				.add("s.c", "0").rm("s.d").message("m2(merge)").create();
+
+		Git git = Git.wrap(db);
+		git.checkout().setName("master").call();
+		modifyWorktree(worktreeState, "f", "side");
+		modifyIndex(indexState, "f", "side");
+
+		ResolveMerger merger = (ResolveMerger) strategy.newMerger(db,
+				worktreeState == WorktreeState.Bare);
+		if (worktreeState != WorktreeState.Bare)
+			merger.setWorkingTreeIterator(new FileTreeIterator(db));
+		try {
+			boolean expectSuccess = true;
+			if (!(indexState == IndexState.Bare
+					|| indexState == IndexState.Missing || indexState == IndexState.SameAsHead))
+				// index is dirty
+				expectSuccess = false;
+			else if (worktreeState == WorktreeState.DifferentFromHeadAndOther
+					|| worktreeState == WorktreeState.SameAsOther)
+				expectSuccess = false;
+			assertEquals(Boolean.valueOf(expectSuccess),
+					Boolean.valueOf(merger.merge(new RevCommit[] { m2, s2 })));
+			assertEquals(MergeStrategy.RECURSIVE, strategy);
+			if (!expectSuccess)
+				// if the merge was not successful skip testing the state of
+				// index and workingtree
+				return;
+			assertEquals(
+					"1-master-r\n2\n3-side-r",
+					contentAsString(db, merger.getResultTreeId(), "f"));
+			if (indexState != IndexState.Bare)
+				assertEquals(
+						"[f, mode:100644, content:1-master-r\n2\n3-side-r\n][m.c, mode:100644, content:0][m.m, mode:100644, content:1][s.c, mode:100644, content:0][s.m, mode:100644, content:1]",
+						indexState(RepositoryTestCase.CONTENT));
+			if (worktreeState != WorktreeState.Bare
+					&& worktreeState != WorktreeState.Missing) {
+				assertEquals(
+						"1-master-r\n2\n3-side-r\n",
+						read("f"));
+				assertTrue(check("s.c"));
+				assertFalse(check("s.d"));
+				assertTrue(check("s.m"));
+				assertTrue(check("m.c"));
+				assertFalse(check("m.d"));
+				assertTrue(check("m.m"));
+			}
+		} catch (NoMergeBaseException e) {
+			assertEquals(MergeStrategy.RESOLVE, strategy);
+			assertEquals(e.getReason(),
+					MergeBaseFailureReason.MULTIPLE_MERGE_BASES_NOT_SUPPORTED);
+		}
+	}
+
 	@Theory
 	/**
 	 * Merging m2,s2 from the following topology. The same file is modified

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

@@ -212,6 +212,12 @@ public class RecursiveMerger extends ResolveMerger {
 			inCore = oldIncore;
 			dircache = oldDircache;
 			workingTreeIterator = oldWTreeIt;
+			toBeCheckedOut.clear();
+			toBeDeleted.clear();
+			modifiedFiles.clear();
+			unmergedPaths.clear();
+			mergeResults.clear();
+			failingPaths.clear();
 		}
 		return currentBase;
 	}