Add support for --no-ff while merging

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

org.eclipse.jgit.pgm.test/tst/org/eclipse/jgit/pgm/MergeTest.java

@@ -42,8 +42,8 @@
  */
 package org.eclipse.jgit.pgm;
 
-import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
 
 import org.eclipse.jgit.api.Git;
 import org.eclipse.jgit.lib.CLIRepositoryTestCase;
@@ -82,7 +82,8 @@ public class MergeTest extends CLIRepositoryTestCase {
 		git.commit().setMessage("commit").call();
 		git.checkout().setName("side").call();
 
-		assertEquals("Fast-forward", execute("git merge master")[0]);
+		assertArrayEquals(new String[] { "Updating 6fd41be..26a81a1",
+				"Fast-forward", "" }, execute("git merge master"));
 	}
 
 	@Test
@@ -120,4 +121,58 @@ public class MergeTest extends CLIRepositoryTestCase {
 						"" },
 				execute("git merge master --squash"));
 	}
+
+	@Test
+	public void testNoFastForward() throws Exception {
+		git.branchCreate().setName("side").call();
+		writeTrashFile("file", "master");
+		git.add().addFilepattern("file").call();
+		git.commit().setMessage("commit").call();
+		git.checkout().setName("side").call();
+
+		assertEquals("Merge made by the 'recursive' strategy.",
+				execute("git merge master --no-ff")[0]);
+		assertArrayEquals(new String[] {
+				"commit 6db23724012376e8407fc24b5da4277a9601be81", //
+				"Author: GIT_COMMITTER_NAME <GIT_COMMITTER_EMAIL>", //
+				"Date:   Sat Aug 15 20:12:58 2009 -0330", //
+				"", //
+				"    Merge branch 'master' into side", //
+				"", //
+				"commit 6fd41be26b7ee41584dd997f665deb92b6c4c004", //
+				"Author: GIT_COMMITTER_NAME <GIT_COMMITTER_EMAIL>", //
+				"Date:   Sat Aug 15 20:12:58 2009 -0330", //
+				"", //
+				"    initial commit", //
+				"", //
+				"commit 26a81a1c6a105551ba703a8b6afc23994cacbae1", //
+				"Author: GIT_COMMITTER_NAME <GIT_COMMITTER_EMAIL>", //
+				"Date:   Sat Aug 15 20:12:58 2009 -0330", //
+				"", //
+				"    commit", //
+				"", //
+				""
+		}, execute("git log"));
+	}
+
+	@Test
+	public void testNoFastForwardAndSquash() throws Exception {
+		assertEquals("fatal: You cannot combine --squash with --no-ff.",
+				execute("git merge master --no-ff --squash")[0]);
+	}
+
+	@Test
+	public void testFastForwardOnly() throws Exception {
+		git.branchCreate().setName("side").call();
+		writeTrashFile("file", "master");
+		git.add().addFilepattern("file").call();
+		git.commit().setMessage("commit#1").call();
+		git.checkout().setName("side").call();
+		writeTrashFile("file", "side");
+		git.add().addFilepattern("file").call();
+		git.commit().setMessage("commit#2").call();
+
+		assertEquals("fatal: Not possible to fast-forward, aborting.",
+				execute("git merge master --ff-only")[0]);
+	}
 }

org.eclipse.jgit.pgm/resources/org/eclipse/jgit/pgm/CLIText.properties

@@ -18,6 +18,7 @@ branchNotFound=branch '{0}' not found.
 cacheTreePathInfo="{0}": {1} entries, {2} children
 cannotBeRenamed={0} cannot be renamed
 cannotChekoutNoHeadsAdvertisedByRemote=cannot checkout; no HEAD advertised by remote
+cannotCombineSquashWithNoff=You cannot combine --squash with --no-ff.
 cannotCreateCommand=Cannot create command {0}
 cannotCreateOutputStream=cannot create output stream
 cannotDeatchHEAD=Cannot detach HEAD
@@ -55,6 +56,7 @@ failedToLockTag=Failed to lock tag {0}: {1}
 fatalError=fatal: {0}
 fatalThisProgramWillDestroyTheRepository=fatal: This program will destroy the repository\nfatal:\nfatal:\nfatal:    {0}\nfatal:\nfatal: To continue, add {1} to the command line\nfatal:
 fileIsRequired=argument file is required
+ffNotPossibleAborting=Not possible to fast-forward, aborting.
 forcedUpdate=forced update
 fromURI=From {0}
 initializedEmptyGitRepositoryIn=Initialized empty Git repository in {0}
@@ -160,6 +162,7 @@ unknownMergeStrategy=unknown merge strategy {0} specified
 unmergedPaths=Unmerged paths:
 unsupportedOperation=Unsupported operation: {0}
 untrackedFiles=Untracked files:
+updating=Updating {0}..{1}
 usage_Blame=Show what revision and author last modified each line
 usage_CommandLineClientForamazonsS3Service=Command line client for Amazon's S3 service
 usage_CommitAll=commit all modified and deleted files

org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/CLIText.java

@@ -86,6 +86,7 @@ public class CLIText extends TranslationBundle {
 	/***/ public String configFileNotFound;
 	/***/ public String cannotBeRenamed;
 	/***/ public String cannotChekoutNoHeadsAdvertisedByRemote;
+	/***/ public String cannotCombineSquashWithNoff;
 	/***/ public String cannotCreateCommand;
 	/***/ public String cannotCreateOutputStream;
 	/***/ public String cannotDeatchHEAD;
@@ -122,6 +123,7 @@ public class CLIText extends TranslationBundle {
 	/***/ public String fatalError;
 	/***/ public String fatalThisProgramWillDestroyTheRepository;
 	/***/ public String fileIsRequired;
+	/***/ public String ffNotPossibleAborting;
 	/***/ public String forcedUpdate;
 	/***/ public String fromURI;
 	/***/ public String initializedEmptyGitRepositoryIn;
@@ -221,5 +223,6 @@ public class CLIText extends TranslationBundle {
 	/***/ public String unmergedPaths;
 	/***/ public String unsupportedOperation;
 	/***/ public String untrackedFiles;
+	/***/ public String updating;
 	/***/ public String warningNoCommitGivenOnCommandLine;
 }

org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/Merge.java

@@ -43,14 +43,22 @@
 
 package org.eclipse.jgit.pgm;
 
+import java.io.IOException;
 import java.text.MessageFormat;
 import java.util.Map;
 
 import org.eclipse.jgit.api.Git;
+import org.eclipse.jgit.api.MergeCommand;
 import org.eclipse.jgit.api.MergeResult;
+import org.eclipse.jgit.api.MergeCommand.FastForwardMode;
+import org.eclipse.jgit.lib.AnyObjectId;
+import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.merge.MergeStrategy;
 import org.eclipse.jgit.merge.ResolveMerger.MergeFailureReason;
+import org.eclipse.jgit.revwalk.RevCommit;
+import org.eclipse.jgit.revwalk.RevWalk;
 import org.kohsuke.args4j.Argument;
 import org.kohsuke.args4j.Option;
 
@@ -68,8 +76,23 @@ class Merge extends TextBuiltin {
 	@Argument(required = true)
 	private String ref;
 
+	@Option(name = "--ff")
+	private FastForwardMode ff = FastForwardMode.FF;
+
+	@Option(name = "--no-ff")
+	void noff(@SuppressWarnings("unused") final boolean ignored) {
+		ff = FastForwardMode.NO_FF;
+	}
+
+	@Option(name = "--ff-only")
+	void ffonly(@SuppressWarnings("unused") final boolean ignored) {
+		ff = FastForwardMode.FF_ONLY;
+	}
+
 	@Override
 	protected void run() throws Exception {
+		if (squash && ff == FastForwardMode.NO_FF)
+			throw die(CLIText.get().cannotCombineSquashWithNoff);
 		// determine the merge strategy
 		if (strategyName != null) {
 			mergeStrategy = MergeStrategy.get(strategyName);
@@ -79,14 +102,21 @@ class Merge extends TextBuiltin {
 		}
 
 		// determine the other revision we want to merge with HEAD
+		final Ref srcRef = db.getRef(ref);
 		final ObjectId src = db.resolve(ref + "^{commit}");
 		if (src == null)
 			throw die(MessageFormat.format(
 					CLIText.get().refDoesNotExistOrNoCommit, ref));
 
+		Ref oldHead = db.getRef(Constants.HEAD);
 		Git git = new Git(db);
-		MergeResult result = git.merge().setStrategy(mergeStrategy)
-				.setSquash(squash).include(src).call();
+		MergeCommand mergeCmd = git.merge().setStrategy(mergeStrategy)
+				.setSquash(squash).setFastForward(ff);
+		if (srcRef != null)
+			mergeCmd.include(srcRef);
+		else
+			mergeCmd.include(src);
+		MergeResult result = mergeCmd.call();
 
 		switch (result.getMergeStatus()) {
 		case ALREADY_UP_TO_DATE:
@@ -95,6 +125,10 @@ class Merge extends TextBuiltin {
 			outw.println(CLIText.get().alreadyUpToDate);
 			break;
 		case FAST_FORWARD:
+			ObjectId oldHeadId = oldHead.getObjectId();
+			outw.println(MessageFormat.format(CLIText.get().updating, oldHeadId
+					.abbreviate(7).name(), result.getNewHead().abbreviate(7)
+					.name()));
 			outw.println(result.getMergeStatus().toString());
 			break;
 		case CONFLICTING:
@@ -119,15 +153,32 @@ class Merge extends TextBuiltin {
 				}
 			break;
 		case MERGED:
-			outw.println(MessageFormat.format(CLIText.get().mergeMadeBy,
-					mergeStrategy.getName()));
+			String name;
+			if (!isMergedInto(oldHead, src))
+				name = mergeStrategy.getName();
+			else
+				name = "recursive";
+			outw.println(MessageFormat.format(CLIText.get().mergeMadeBy, name));
 			break;
 		case MERGED_SQUASHED:
 			outw.println(CLIText.get().mergedSquashed);
 			break;
+		case ABORTED:
+			throw die(CLIText.get().ffNotPossibleAborting);
 		case NOT_SUPPORTED:
 			outw.println(MessageFormat.format(
 					CLIText.get().unsupportedOperation, result.toString()));
 		}
 	}
+
+	private boolean isMergedInto(Ref oldHead, AnyObjectId src)
+			throws IOException {
+		RevWalk revWalk = new RevWalk(db);
+		ObjectId oldHeadObjectId = oldHead.getPeeledObjectId();
+		if (oldHeadObjectId == null)
+			oldHeadObjectId = oldHead.getObjectId();
+		RevCommit oldHeadCommit = revWalk.lookupCommit(oldHeadObjectId);
+		RevCommit srcCommit = revWalk.lookupCommit(src);
+		return revWalk.isMergedInto(oldHeadCommit, srcCommit);
+	}
 }

org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties

@@ -31,6 +31,7 @@ branchNameInvalid=Branch name {0} is not allowed
 cachedPacksPreventsIndexCreation=Using cached packs prevents index creation
 cannotBeCombined=Cannot be combined.
 cannotBeRecursiveWhenTreesAreIncluded=TreeWalk shouldn't be recursive when tree objects are included.
+cannotCombineSquashWithNoff=Cannot combine --squash with --no-ff.
 cannotCombineTreeFilterWithRevFilter=Cannot combine TreeFilter {0} with RevFilter {1}.
 cannotCommitOnARepoWithState=Cannot commit on a repo with state: {0}
 cannotCommitWriteTo=Cannot commit write to {0}

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;
+	}
 }

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

@@ -152,6 +152,20 @@ public class MergeResult {
 				return false;
 			}
 		},
+		/**
+		 * @since 2.2
+		 */
+		ABORTED {
+			@Override
+			public String toString() {
+				return "Aborted";
+			}
+
+			@Override
+			public boolean isSuccessful() {
+				return false;
+			}
+		},
 		/** */
 		NOT_SUPPORTED {
 			@Override

org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java

@@ -91,6 +91,7 @@ public class JGitText extends TranslationBundle {
 	/***/ public String cachedPacksPreventsIndexCreation;
 	/***/ public String cannotBeCombined;
 	/***/ public String cannotBeRecursiveWhenTreesAreIncluded;
+	/***/ public String cannotCombineSquashWithNoff;
 	/***/ public String cannotCombineTreeFilterWithRevFilter;
 	/***/ public String cannotCommitOnARepoWithState;
 	/***/ public String cannotCommitWriteTo;