Add CHERRY_PICK_HEAD for cherry-pick conflicts

Add handling of CHERRY_PICK_HEAD file in .git (similar to MERGE_HEAD),
which is written in case of a conflicting cherry-pick merge.

It is used so that Repository.getRepositoryState can return the new
states CHERRY_PICKING and CHERRY_PICKING_RESOLVED. These states, as well
as CHERRY_PICK_HEAD can be used in EGit to properly show the merge tool.

Also, in case of a conflict, MERGE_MSG is written with the original
commit message and a "Conflicts" section appended. This way, the
cherry-picked message is not lost and can later be re-used in the commit
dialog.

Bug: 339092
Change-Id: I947967fdc2f1d55016c95106b104c2afcc9797a1
Signed-off-by: Robin Stocker <robin@nibor.org>
Signed-off-by: Chris Aniszczyk <caniszczyk@gmail.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/api/CherryPickCommandTest.java

@@ -44,14 +44,17 @@ package org.eclipse.jgit.api;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
 
 import java.io.File;
 import java.io.IOException;
 import java.util.Iterator;
 
 import org.eclipse.jgit.api.CherryPickResult.CherryPickStatus;
+import org.eclipse.jgit.api.ResetCommand.ResetType;
 import org.eclipse.jgit.api.errors.GitAPIException;
 import org.eclipse.jgit.api.errors.JGitInternalException;
+import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.RepositoryState;
 import org.eclipse.jgit.lib.RepositoryTestCase;
 import org.eclipse.jgit.merge.ResolveMerger.MergeFailureReason;
@@ -130,6 +133,55 @@ public class CherryPickCommandTest extends RepositoryTestCase {
 				MergeFailureReason.DIRTY_WORKTREE);
 	}
 
+	@Test
+	public void testCherryPickConflictResolution() throws Exception {
+		Git git = new Git(db);
+		RevCommit sideCommit = prepareCherryPick(git);
+
+		CherryPickResult result = git.cherryPick().include(sideCommit.getId())
+				.call();
+
+		assertEquals(CherryPickStatus.CONFLICTING, result.getStatus());
+		assertTrue(new File(db.getDirectory(), Constants.MERGE_MSG).exists());
+		assertEquals("side\n\nConflicts:\n\ta\n", db.readMergeCommitMsg());
+		assertTrue(new File(db.getDirectory(), Constants.CHERRY_PICK_HEAD)
+				.exists());
+		assertEquals(sideCommit.getId(), db.readCherryPickHead());
+		assertEquals(RepositoryState.CHERRY_PICKING, db.getRepositoryState());
+
+		// Resolve
+		writeTrashFile("a", "a");
+		git.add().addFilepattern("a").call();
+
+		assertEquals(RepositoryState.CHERRY_PICKING_RESOLVED,
+				db.getRepositoryState());
+
+		git.commit().setOnly("a").setMessage("resolve").call();
+
+		assertEquals(RepositoryState.SAFE, db.getRepositoryState());
+	}
+
+	@Test
+	public void testCherryPickConflictReset() throws Exception {
+		Git git = new Git(db);
+
+		RevCommit sideCommit = prepareCherryPick(git);
+
+		CherryPickResult result = git.cherryPick().include(sideCommit.getId())
+				.call();
+
+		assertEquals(CherryPickStatus.CONFLICTING, result.getStatus());
+		assertEquals(RepositoryState.CHERRY_PICKING, db.getRepositoryState());
+		assertTrue(new File(db.getDirectory(), Constants.CHERRY_PICK_HEAD)
+				.exists());
+
+		git.reset().setMode(ResetType.MIXED).setRef("HEAD").call();
+
+		assertEquals(RepositoryState.SAFE, db.getRepositoryState());
+		assertFalse(new File(db.getDirectory(), Constants.CHERRY_PICK_HEAD)
+				.exists());
+	}
+
 	private RevCommit prepareCherryPick(final Git git) throws Exception {
 		// create, add and commit file a
 		writeTrashFile("a", "a");

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

@@ -60,6 +60,7 @@ import org.eclipse.jgit.lib.ObjectIdRef;
 import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.lib.Ref.Storage;
 import org.eclipse.jgit.lib.Repository;
+import org.eclipse.jgit.merge.MergeMessageFormatter;
 import org.eclipse.jgit.merge.MergeStrategy;
 import org.eclipse.jgit.merge.ResolveMerger;
 import org.eclipse.jgit.revwalk.RevCommit;
@@ -150,7 +151,15 @@ public class CherryPickCommand extends GitCommand<CherryPickResult> {
 					if (merger.failed())
 						return new CherryPickResult(merger.getFailingPaths());
 
-					// merge conflicts
+					// there are merge conflicts
+
+					String message = new MergeMessageFormatter()
+							.formatWithConflicts(srcCommit.getFullMessage(),
+									merger.getUnmergedPaths());
+
+					repo.writeCherryPickHead(srcCommit.getId());
+					repo.writeMergeCommitMsg(message);
+
 					return CherryPickResult.CONFLICT;
 				}
 			}

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

@@ -233,6 +233,9 @@ public class CommitCommand extends GitCommand<RevCommit> {
 								// used for merge commits
 								repo.writeMergeCommitMsg(null);
 								repo.writeMergeHeads(null);
+							} else if (state == RepositoryState.CHERRY_PICKING_RESOLVED) {
+								repo.writeMergeCommitMsg(null);
+								repo.writeCherryPickHead(null);
 							}
 							return revCommit;
 						}

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

@@ -399,6 +399,9 @@ public class RebaseCommand extends GitCommand<RebaseResult> {
 				Constants.CHARACTER_ENCODING));
 		createFile(rebaseDir, STOPPED_SHA, repo.newObjectReader().abbreviate(
 				commitToPick).name());
+		// Remove cherry pick state file created by CherryPickCommand, it's not
+		// needed for rebase
+		repo.writeCherryPickHead(null);
 		return new RebaseResult(commitToPick);
 	}
 
@@ -744,6 +747,7 @@ public class RebaseCommand extends GitCommand<RebaseResult> {
 			}
 			// cleanup the files
 			FileUtils.delete(rebaseDir, FileUtils.RECURSIVE);
+			repo.writeCherryPickHead(null);
 			return result;
 
 		} finally {

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

@@ -129,11 +129,12 @@ public class ResetCommand extends GitCommand<Ref> {
 		RevCommit commit;
 
 		try {
-			boolean merging = false;
-			if (repo.getRepositoryState().equals(RepositoryState.MERGING)
-					|| repo.getRepositoryState().equals(
-							RepositoryState.MERGING_RESOLVED))
-				merging = true;
+			RepositoryState state = repo.getRepositoryState();
+			final boolean merging = state.equals(RepositoryState.MERGING)
+					|| state.equals(RepositoryState.MERGING_RESOLVED);
+			final boolean cherryPicking = state
+					.equals(RepositoryState.CHERRY_PICKING)
+					|| state.equals(RepositoryState.CHERRY_PICKING_RESOLVED);
 
 			// resolve the ref to a commit
 			final ObjectId commitId;
@@ -183,8 +184,12 @@ public class ResetCommand extends GitCommand<Ref> {
 
 			}
 
-			if (mode != ResetType.SOFT && merging)
-				resetMerge();
+			if (mode != ResetType.SOFT) {
+				if (merging)
+					resetMerge();
+				else if (cherryPicking)
+					resetCherryPick();
+			}
 
 			setCallable(false);
 			r = ru.getRef();
@@ -255,4 +260,9 @@ public class ResetCommand extends GitCommand<Ref> {
 		repo.writeMergeCommitMsg(null);
 	}
 
+	private void resetCherryPick() throws IOException {
+		repo.writeCherryPickHead(null);
+		repo.writeMergeCommitMsg(null);
+	}
+
 }

org.eclipse.jgit/src/org/eclipse/jgit/lib/Constants.java

@@ -536,6 +536,9 @@ public final class Constants {
 	/** name of the file containing the IDs of the parents of a merge commit */
 	public static final String MERGE_HEAD = "MERGE_HEAD";
 
+	/** name of the file containing the ID of a cherry pick commit in case of conflicts */
+	public static final String CHERRY_PICK_HEAD = "CHERRY_PICK_HEAD";
+
 	/**
 	 * name of the ref ORIG_HEAD used by certain commands to store the original
 	 * value of HEAD

org.eclipse.jgit/src/org/eclipse/jgit/lib/Repository.java

@@ -922,7 +922,7 @@ public abstract class Repository {
 			return RepositoryState.REBASING_MERGE;
 
 		// Both versions
-		if (new File(getDirectory(), "MERGE_HEAD").exists()) {
+		if (new File(getDirectory(), Constants.MERGE_HEAD).exists()) {
 			// we are merging - now check whether we have unmerged paths
 			try {
 				if (!readDirCache().hasUnmergedPaths()) {
@@ -941,6 +941,20 @@ public abstract class Repository {
 		if (new File(getDirectory(), "BISECT_LOG").exists())
 			return RepositoryState.BISECTING;
 
+		if (new File(getDirectory(), Constants.CHERRY_PICK_HEAD).exists()) {
+			try {
+				if (!readDirCache().hasUnmergedPaths()) {
+					// no unmerged paths
+					return RepositoryState.CHERRY_PICKING_RESOLVED;
+				}
+			} catch (IOException e) {
+				// fall through to CHERRY_PICKING
+				e.printStackTrace();
+			}
+
+			return RepositoryState.CHERRY_PICKING;
+		}
+
 		return RepositoryState.SAFE;
 	}
 
@@ -1192,4 +1206,60 @@ public abstract class Repository {
 			FileUtils.delete(mergeHeadFile);
 		}
 	}
+
+	/**
+	 * Return the information stored in the file $GIT_DIR/CHERRY_PICK_HEAD.
+	 *
+	 * @return object id from CHERRY_PICK_HEAD file or {@code null} if this file
+	 *         doesn't exist. Also if the file exists but is empty {@code null}
+	 *         will be returned
+	 * @throws IOException
+	 * @throws NoWorkTreeException
+	 *             if this is bare, which implies it has no working directory.
+	 *             See {@link #isBare()}.
+	 */
+	public ObjectId readCherryPickHead() throws IOException,
+			NoWorkTreeException {
+		if (isBare() || getDirectory() == null)
+			throw new NoWorkTreeException();
+
+		File mergeHeadFile = new File(getDirectory(),
+				Constants.CHERRY_PICK_HEAD);
+		byte[] raw;
+		try {
+			raw = IO.readFully(mergeHeadFile);
+		} catch (FileNotFoundException notFound) {
+			return null;
+		}
+
+		if (raw.length == 0)
+			return null;
+
+		return ObjectId.fromString(raw, 0);
+	}
+
+	/**
+	 * Write cherry pick commit into $GIT_DIR/CHERRY_PICK_HEAD. This is used in
+	 * case of conflicts to store the cherry which was tried to be picked.
+	 *
+	 * @param head
+	 *            an object id of the cherry commit or <code>null</code> to
+	 *            delete the file
+	 * @throws IOException
+	 */
+	public void writeCherryPickHead(ObjectId head) throws IOException {
+		File cherryPickHeadFile = new File(gitDir, Constants.CHERRY_PICK_HEAD);
+		if (head != null) {
+			BufferedOutputStream bos = new BufferedOutputStream(
+					new FileOutputStream(cherryPickHeadFile));
+			try {
+				head.copyTo(bos);
+				bos.write('\n');
+			} finally {
+				bos.close();
+			}
+		} else {
+			FileUtils.delete(cherryPickHeadFile, FileUtils.SKIP_MISSING);
+		}
+	}
 }

org.eclipse.jgit/src/org/eclipse/jgit/lib/RepositoryState.java

@@ -93,6 +93,26 @@ public enum RepositoryState {
 		public String getDescription() { return JGitText.get().repositoryState_merged; }
 	},
 
+	/** An unfinished cherry-pick. Must resolve or reset before continuing normally
+	 */
+	CHERRY_PICKING {
+		public boolean canCheckout() { return false; }
+		public boolean canResetHead() { return true; }
+		public boolean canCommit() { return false; }
+		public String getDescription() { return JGitText.get().repositoryState_conflicts; }
+	},
+
+	/**
+	 * A cherry-pick where all conflicts have been resolved. The index does not
+	 * contain any unmerged paths.
+	 */
+	CHERRY_PICKING_RESOLVED {
+		public boolean canCheckout() { return true; }
+		public boolean canResetHead() { return true; }
+		public boolean canCommit() { return true; }
+		public String getDescription() { return JGitText.get().repositoryState_merged; }
+	},
+
 	/**
 	 * An unfinished rebase or am. Must resolve, skip or abort before normal work can take place
 	 */

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

@@ -123,6 +123,27 @@ public class MergeMessageFormatter {
 		return sb.toString();
 	}
 
+	/**
+	 * Add section with conflicting paths to merge message.
+	 *
+	 * @param message
+	 *            the original merge message
+	 * @param conflictingPaths
+	 *            the paths with conflicts
+	 * @return merge message with conflicting paths added
+	 */
+	public String formatWithConflicts(String message,
+			List<String> conflictingPaths) {
+		StringBuilder sb = new StringBuilder(message);
+		if (!message.endsWith("\n"))
+			sb.append("\n");
+		sb.append("\n");
+		sb.append("Conflicts:\n");
+		for (String conflictingPath : conflictingPaths)
+			sb.append('\t').append(conflictingPath).append('\n');
+		return sb.toString();
+	}
+
 	private static String joinNames(List<String> names, String singular,
 			String plural) {
 		if (names.size() == 1)

org.eclipse.jgit/src/org/eclipse/jgit/storage/file/RefDirectory.java

@@ -130,7 +130,8 @@ public class RefDirectory extends RefDatabase {
 
 	/** The names of the additional refs supported by this class */
 	private static final String[] additionalRefsNames = new String[] {
-			Constants.MERGE_HEAD, Constants.FETCH_HEAD, Constants.ORIG_HEAD };
+			Constants.MERGE_HEAD, Constants.FETCH_HEAD, Constants.ORIG_HEAD,
+			Constants.CHERRY_PICK_HEAD };
 
 	private final FileRepository parent;