Add support for --no-ff while merging

Bug: 394432
Change-Id: I373128c0ba949f9b24248874f77f3d68b50ccfd1
Signed-off-by: Chris Aniszczyk <zx@twitter.com>

1 files changed, 66 insertions, 10 deletions

diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/api/MergeCommand.java b/org.eclipse.jgit/src/org/eclipse/jgit/api/MergeCommand.java
index 3ca861c06c..a884c70cb0 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/api/MergeCommand.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/api/MergeCommand.java
@@ -99,6 +99,30 @@ public class MergeCommand extends GitCommand<MergeResult> {
 
 	private boolean squash;
 
+	private FastForwardMode fastForwardMode = FastForwardMode.FF;
+
+	/**
+	 * The modes available for fast forward merges (corresponding to the --ff,
+	 * --no-ff and --ff-only options).
+	 */
+	public enum FastForwardMode {
+		/**
+		 * Corresponds to the default --ff option (for a fast forward update the
+		 * branch pointer only).
+		 */
+		FF,
+		/**
+		 * Corresponds to the --no-ff option (create a merge commit even for a
+		 * fast forward).
+		 */
+		NO_FF,
+		/**
+		 * Corresponds to the --ff-only option (abort unless the merge is a fast
+		 * forward).
+		 */
+		FF_ONLY;
+	}
+
 	/**
 	 * @param repo
 	 */
@@ -118,14 +142,7 @@ public class MergeCommand extends GitCommand<MergeResult> {
 			ConcurrentRefUpdateException, CheckoutConflictException,
 			InvalidMergeHeadsException, WrongRepositoryStateException, NoMessageException {
 		checkCallable();
-
-		if (commits.size() != 1)
-			throw new InvalidMergeHeadsException(
-					commits.isEmpty() ? JGitText.get().noMergeHeadSpecified
-							: MessageFormat.format(
-									JGitText.get().mergeStrategyDoesNotSupportHeads,
-									mergeStrategy.getName(),
-									Integer.valueOf(commits.size())));
+		checkParameters();
 
 		RevWalk revWalk = null;
 		DirCacheCheckout dco = null;
@@ -179,7 +196,8 @@ public class MergeCommand extends GitCommand<MergeResult> {
 				return new MergeResult(headCommit, srcCommit, new ObjectId[] {
 						headCommit, srcCommit },
 						MergeStatus.ALREADY_UP_TO_DATE, mergeStrategy, null, null);
-			} else if (revWalk.isMergedInto(headCommit, srcCommit)) {
+			} else if (revWalk.isMergedInto(headCommit, srcCommit)
+					&& fastForwardMode == FastForwardMode.FF) {
 				// FAST_FORWARD detected: skip doing a real merge but only
 				// update HEAD
 				refLogMessage.append(": " + MergeStatus.FAST_FORWARD);
@@ -210,6 +228,11 @@ public class MergeCommand extends GitCommand<MergeResult> {
 						headCommit, srcCommit }, mergeStatus, mergeStrategy,
 						null, msg);
 			} else {
+				if (fastForwardMode == FastForwardMode.FF_ONLY) {
+					return new MergeResult(headCommit, srcCommit,
+							new ObjectId[] { headCommit, srcCommit },
+							MergeStatus.ABORTED, mergeStrategy, null, null);
+				}
 				String mergeMessage = "";
 				if (!squash) {
 					mergeMessage = new MergeMessageFormatter().format(
@@ -241,7 +264,10 @@ public class MergeCommand extends GitCommand<MergeResult> {
 				} else
 					noProblems = merger.merge(headCommit, srcCommit);
 				refLogMessage.append(": Merge made by ");
-				refLogMessage.append(mergeStrategy.getName());
+				if (!revWalk.isMergedInto(headCommit, srcCommit))
+					refLogMessage.append(mergeStrategy.getName());
+				else
+					refLogMessage.append("recursive");
 				refLogMessage.append('.');
 				if (noProblems) {
 					dco = new DirCacheCheckout(repo,
@@ -305,6 +331,21 @@ public class MergeCommand extends GitCommand<MergeResult> {
 		}
 	}
 
+	private void checkParameters() throws InvalidMergeHeadsException {
+		if (squash && fastForwardMode == FastForwardMode.NO_FF) {
+			throw new JGitInternalException(
+					JGitText.get().cannotCombineSquashWithNoff);
+		}
+
+		if (commits.size() != 1)
+			throw new InvalidMergeHeadsException(
+					commits.isEmpty() ? JGitText.get().noMergeHeadSpecified
+							: MessageFormat.format(
+									JGitText.get().mergeStrategyDoesNotSupportHeads,
+									mergeStrategy.getName(),
+									Integer.valueOf(commits.size())));
+	}
+
 	private void updateHead(StringBuilder refLogMessage, ObjectId newHeadId,
 			ObjectId oldHeadID) throws IOException,
 			ConcurrentRefUpdateException {
@@ -392,4 +433,19 @@ public class MergeCommand extends GitCommand<MergeResult> {
 		this.squash = squash;
 		return this;
 	}
+
+	/**
+	 * Sets the fast forward mode.
+	 *
+	 * @param fastForwardMode
+	 *            corresponds to the --ff/--no-ff/--ff-only options. --ff is the
+	 *            default option.
+	 * @return {@code this}
+	 * @since 2.2
+	 */
+	public MergeCommand setFastForward(FastForwardMode fastForwardMode) {
+		checkCallable();
+		this.fastForwardMode = fastForwardMode;
+		return this;
+	}
 }