Merge changes from topic 'rebase_compatibility'

* changes:
  RebaseCommand: tighten check for --preserve-merges on --continue
  RebaseCommand: use orig-head to abort
  RebaseCommand: use orig-head in addition to head

org.eclipse.jgit/src/org/eclipse/jgit/api/RebaseCommand.java

@@ -162,7 +162,10 @@ public class RebaseCommand extends GitCommand<RebaseResult> {
 
 	private static final String PATCH = "patch"; //$NON-NLS-1$
 
-	private static final String REBASE_HEAD = "head"; //$NON-NLS-1$
+	private static final String REBASE_HEAD = "orig-head"; //$NON-NLS-1$
+
+	/** Pre git 1.7.6 file name for {@link #REBASE_HEAD}. */
+	private static final String REBASE_HEAD_LEGACY = "head"; //$NON-NLS-1$
 
 	private static final String AMEND = "amend"; //$NON-NLS-1$
 
@@ -177,6 +180,10 @@ public class RebaseCommand extends GitCommand<RebaseResult> {
 	/**
 	 * The folder containing the hashes of (potentially) rewritten commits when
 	 * --preserve-merges is used.
+	 * <p>
+	 * Native git rebase --merge uses a <em>file</em> of that name to record
+	 * commits to copy notes at the end of the whole rebase.
+	 * </p>
 	 */
 	private static final String REWRITTEN = "rewritten"; //$NON-NLS-1$
 
@@ -289,7 +296,7 @@ public class RebaseCommand extends GitCommand<RebaseResult> {
 				}
 				this.upstreamCommit = walk.parseCommit(repo
 						.resolve(upstreamCommitId));
-				preserveMerges = rebaseState.getRewrittenDir().exists();
+				preserveMerges = rebaseState.getRewrittenDir().isDirectory();
 				break;
 			case BEGIN:
 				autoStash();
@@ -1120,6 +1127,7 @@ public class RebaseCommand extends GitCommand<RebaseResult> {
 
 		repo.writeOrigHead(headId);
 		rebaseState.createFile(REBASE_HEAD, headId.name());
+		rebaseState.createFile(REBASE_HEAD_LEGACY, headId.name());
 		rebaseState.createFile(HEAD_NAME, headName);
 		rebaseState.createFile(ONTO, upstreamCommit.name());
 		rebaseState.createFile(ONTO_NAME, upstreamCommitName);
@@ -1336,8 +1344,8 @@ public class RebaseCommand extends GitCommand<RebaseResult> {
 
 	private RebaseResult abort(RebaseResult result) throws IOException,
 			GitAPIException {
+		ObjectId origHead = getOriginalHead();
 		try {
-			ObjectId origHead = repo.readOrigHead();
 			String commitId = origHead != null ? origHead.name() : null;
 			monitor.beginTask(MessageFormat.format(
 					JGitText.get().abortingRebase, commitId),
@@ -1376,7 +1384,7 @@ public class RebaseCommand extends GitCommand<RebaseResult> {
 				// update the HEAD
 				res = refUpdate.link(headName);
 			} else {
-				refUpdate.setNewObjectId(repo.readOrigHead());
+				refUpdate.setNewObjectId(origHead);
 				res = refUpdate.forceUpdate();
 
 			}
@@ -1403,6 +1411,19 @@ public class RebaseCommand extends GitCommand<RebaseResult> {
 		}
 	}
 
+	private ObjectId getOriginalHead() throws IOException {
+		try {
+			return ObjectId.fromString(rebaseState.readFile(REBASE_HEAD));
+		} catch (FileNotFoundException e) {
+			try {
+				return ObjectId
+						.fromString(rebaseState.readFile(REBASE_HEAD_LEGACY));
+			} catch (FileNotFoundException ex) {
+				return repo.readOrigHead();
+			}
+		}
+	}
+
 	private boolean checkoutCommit(String headName, RevCommit commit)
 			throws IOException,
 			CheckoutConflictException {