Fix ResolveMerger not to add paths with FileMode 0

When ResolveMerger finds a path where it has to do a content merge it
will try the content merge and if that succeeds it'll add the newly
produced content to the index. For the FileMode of this new index entry
it blindly copies the FileMode it finds for that path in the common base
tree. If by chance the common base tree does not contain this path it'll
try to add FileMode 0 (MISSING) to the index.

One could argue that this can't happen: how can the ResolveMerger
successfully (with no conflicts) merge two contents if there is no
common base? This was due to another bug in ResolveMerger. It failed to
find out that for two files which differ only in the FileMode (e.g. 644
vs. 755) it should not try a content merge.

Change-Id: I7a00fe1a6c610679be475cab8a3f8aa4c08811a1
Signed-off-by: Christian Halstrick <christian.halstrick@sap.com>
Signed-off-by: Robin Rosenberg <robin.rosenberg@dewire.com>

2 files changed, 150 insertions, 7 deletions

diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/api/MergeCommandTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/api/MergeCommandTest.java
index bb90588918..d1aaa0a5f8 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/api/MergeCommandTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/api/MergeCommandTest.java
@@ -1023,6 +1023,81 @@ public class MergeCommandTest extends RepositoryTestCase {
 		assertFalse(folder2.exists());
 	}
 
+	@Test
+	public void testFileModeMerge() throws Exception {
+		Git git = new Git(db);
+
+		writeTrashFile("mergeableMode", "a");
+		setExecutable(git, "mergeableMode", false);
+		writeTrashFile("conflictingModeWithBase", "a");
+		setExecutable(git, "conflictingModeWithBase", false);
+		RevCommit initialCommit = addAllAndCommit(git);
+
+		// switch branch
+		createBranch(initialCommit, "refs/heads/side");
+		checkoutBranch("refs/heads/side");
+		setExecutable(git, "mergeableMode", true);
+		writeTrashFile("conflictingModeNoBase", "b");
+		setExecutable(git, "conflictingModeNoBase", true);
+		RevCommit sideCommit = addAllAndCommit(git);
+
+		// switch branch
+		createBranch(initialCommit, "refs/heads/side2");
+		checkoutBranch("refs/heads/side2");
+		setExecutable(git, "mergeableMode", false);
+		assertFalse(new File(git.getRepository().getWorkTree(),
+				"conflictingModeNoBase").exists());
+		writeTrashFile("conflictingModeNoBase", "b");
+		setExecutable(git, "conflictingModeNoBase", false);
+		addAllAndCommit(git);
+
+		// merge
+		MergeResult result = git.merge().include(sideCommit.getId())
+				.setStrategy(MergeStrategy.RESOLVE).call();
+		assertEquals(MergeStatus.CONFLICTING, result.getMergeStatus());
+		assertTrue(canExecute(git, "mergeableMode"));
+		assertFalse(canExecute(git, "conflictingModeNoBase"));
+	}
+
+	@Test
+	public void testFileModeMergeWithDirtyWorkTree() throws Exception {
+		Git git = new Git(db);
+
+		writeTrashFile("mergeableButDirty", "a");
+		setExecutable(git, "mergeableButDirty", false);
+		RevCommit initialCommit = addAllAndCommit(git);
+
+		// switch branch
+		createBranch(initialCommit, "refs/heads/side");
+		checkoutBranch("refs/heads/side");
+		setExecutable(git, "mergeableButDirty", true);
+		RevCommit sideCommit = addAllAndCommit(git);
+
+		// switch branch
+		createBranch(initialCommit, "refs/heads/side2");
+		checkoutBranch("refs/heads/side2");
+		setExecutable(git, "mergeableButDirty", false);
+		addAllAndCommit(git);
+
+		writeTrashFile("mergeableButDirty", "b");
+
+		// merge
+		MergeResult result = git.merge().include(sideCommit.getId())
+				.setStrategy(MergeStrategy.RESOLVE).call();
+		assertEquals(MergeStatus.FAILED, result.getMergeStatus());
+		assertFalse(canExecute(git, "mergeableButDirty"));
+	}
+
+	private void setExecutable(Git git, String path, boolean executable) {
+		new File(git.getRepository().getWorkTree(), path)
+				.setExecutable(executable);
+		assertEquals(executable, canExecute(git, path));
+	}
+
+	private boolean canExecute(Git git, String path) {
+		return (new File(git.getRepository().getWorkTree(), path).canExecute());
+	}
+
 	private RevCommit addAllAndCommit(final Git git) throws Exception {
 		git.add().addFilepattern(".").call();
 		return git.commit().setMessage("message").call();
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/merge/ResolveMerger.java b/org.eclipse.jgit/src/org/eclipse/jgit/merge/ResolveMerger.java
index b763568951..8211780ca1 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/merge/ResolveMerger.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/merge/ResolveMerger.java
@@ -51,6 +51,7 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.LinkedList;
@@ -378,12 +379,46 @@ public class ResolveMerger extends ThreeWayMerger {
 		if (isIndexDirty())
 			return false;
 
-		if (nonTree(modeO) && modeO == modeT && tw.idEqual(T_OURS, T_THEIRS)) {
-			// OURS and THEIRS are equal: it doesn't matter which one we choose.
-			// OURS is chosen.
-			add(tw.getRawPath(), ours, DirCacheEntry.STAGE_0);
-			// no checkout needed!
-			return true;
+		if (nonTree(modeO) && nonTree(modeT) && tw.idEqual(T_OURS, T_THEIRS)) {
+			// OURS and THEIRS have equal content. Check the file mode
+			if (modeO == modeT) {
+				// content and mode of OURS and THEIRS are equal: it doesn't
+				// matter which one we choose. OURS is chosen.
+				add(tw.getRawPath(), ours, DirCacheEntry.STAGE_0);
+				// no checkout needed!
+				return true;
+			} else {
+				// same content but different mode on OURS and THEIRS.
+				// Try to merge the mode and report an error if this is
+				// not possible.
+				int newMode = mergeFileModes(modeB, modeO, modeT);
+				if (newMode != FileMode.MISSING.getBits()) {
+					if (newMode == modeO)
+						// ours version is preferred
+						add(tw.getRawPath(), ours, DirCacheEntry.STAGE_0);
+					else {
+						// the preferred version THEIRS has a different mode
+						// than ours. Check it out!
+						if (isWorktreeDirty())
+							return false;
+						DirCacheEntry e = add(tw.getRawPath(), theirs,
+								DirCacheEntry.STAGE_0);
+						toBeCheckedOut.put(tw.getPathString(), e);
+					}
+					return true;
+				} else {
+					// FileModes are not mergeable. We found a conflict on modes
+					add(tw.getRawPath(), base, DirCacheEntry.STAGE_1);
+					add(tw.getRawPath(), ours, DirCacheEntry.STAGE_2);
+					add(tw.getRawPath(), theirs, DirCacheEntry.STAGE_3);
+					unmergedPaths.add(tw.getPathString());
+					mergeResults.put(
+							tw.getPathString(),
+							new MergeResult<RawText>(Collections
+									.<RawText> emptyList()));
+				}
+				return true;
+			}
 		}
 
 		if (nonTree(modeO) && modeB == modeT && tw.idEqual(T_BASE, T_THEIRS)) {
@@ -582,7 +617,12 @@ public class ResolveMerger extends ThreeWayMerger {
 			// no conflict occurred, the file will contain fully merged content.
 			// the index will be populated with the new merged version
 			DirCacheEntry dce = new DirCacheEntry(tw.getPathString());
-			dce.setFileMode(tw.getFileMode(0));
+			int newMode = mergeFileModes(tw.getRawMode(0), tw.getRawMode(1),
+					tw.getRawMode(2));
+			// set the mode for the new content. Fall back to REGULAR_FILE if
+			// you can't merge modes of OURS and THEIRS
+			dce.setFileMode((newMode == FileMode.MISSING.getBits()) ? FileMode.REGULAR_FILE
+					: FileMode.fromBits(newMode));
 			dce.setLastModified(of.lastModified());
 			dce.setLength((int) of.length());
 			InputStream is = new FileInputStream(of);
@@ -599,6 +639,34 @@ public class ResolveMerger extends ThreeWayMerger {
 		}
 	}
 
+	/**
+	 * Try to merge filemodes. If only ours or theirs have changed the mode
+	 * (compared to base) we choose that one. If ours and theirs have equal
+	 * modes return that one. If also that is not the case the modes are not
+	 * mergeable. Return {@link FileMode#MISSING} int that case.
+	 *
+	 * @param modeB
+	 *            filemode found in BASE
+	 * @param modeO
+	 *            filemode found in OURS
+	 * @param modeT
+	 *            filemode found in THEIRS
+	 *
+	 * @return the merged filemode or {@link FileMode#MISSING} in case of a
+	 *         conflict
+	 */
+	private int mergeFileModes(int modeB, int modeO, int modeT) {
+		if (modeO == modeT)
+			return modeO;
+		if (modeB == modeO)
+			// Base equal to Ours -> chooses Theirs if that is not missing
+			return (modeT == FileMode.MISSING.getBits()) ? modeO : modeT;
+		if (modeB == modeT)
+			// Base equal to Theirs -> chooses Ours if that is not missing
+			return (modeO == FileMode.MISSING.getBits()) ? modeT : modeO;
+		return FileMode.MISSING.getBits();
+	}
+
 	private static RawText getRawText(ObjectId id, Repository db)
 			throws IOException {
 		if (id.equals(ObjectId.zeroId()))