Add methods which write MERGE_HEAD and MERGE_MSG

Add methods to the Repository class which write into MERGE_HEAD
and MERGE_MSG files. Since we have the read methods in the same
class this seems to be the right place.

Change-Id: I5dd65306ceb06e008fcc71b37ca3a649632ba462
Signed-off-by: Christian Halstrick <christian.halstrick@sap.com>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/MergeHeadMsgTest.java

@@ -0,0 +1,108 @@
+/*
+ * Copyright (C) 2010, Christian Halstrick <christian.halstrick@sap.com>
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+package org.eclipse.jgit.lib;
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.Collections;
+
+public class MergeHeadMsgTest extends RepositoryTestCase {
+	private static final String mergeMsg = "merge a and b";
+
+	private static final String sampleId = "1c6db447abdbb291b25f07be38ea0b1bf94947c5";
+
+	public void testReadWriteMergeHeads() throws IOException {
+		assertEquals(db.readMergeHeads(), null);
+		db.writeMergeHeads(Arrays.asList(ObjectId.zeroId(),
+				ObjectId.fromString(sampleId)));
+		assertEquals(read(new File(db.getDirectory(), "MERGE_HEAD")), "0000000000000000000000000000000000000000\n1c6db447abdbb291b25f07be38ea0b1bf94947c5\n");
+		assertEquals(db.readMergeHeads().size(), 2);
+		assertEquals(db.readMergeHeads().get(0), ObjectId.zeroId());
+		assertEquals(db.readMergeHeads().get(1), ObjectId.fromString(sampleId));
+		// same test again, this time with lower-level io
+		FileOutputStream fos = new FileOutputStream(new File(db.getDirectory(),
+		"MERGE_HEAD"));
+		try {
+			fos.write("0000000000000000000000000000000000000000\n1c6db447abdbb291b25f07be38ea0b1bf94947c5\n".getBytes(Constants.CHARACTER_ENCODING));
+		} finally {
+			fos.close();
+		}
+		assertEquals(db.readMergeHeads().size(), 2);
+		assertEquals(db.readMergeHeads().get(0), ObjectId.zeroId());
+		assertEquals(db.readMergeHeads().get(1), ObjectId.fromString(sampleId));
+		db.writeMergeHeads(Collections.EMPTY_LIST);
+		assertEquals(read(new File(db.getDirectory(), "MERGE_HEAD")), "");
+		assertEquals(db.readMergeHeads(), null);
+		fos = new FileOutputStream(new File(db.getDirectory(),
+				"MERGE_HEAD"));
+		try {
+			fos.write(sampleId.getBytes(Constants.CHARACTER_ENCODING));
+		} finally {
+			fos.close();
+		}
+		assertEquals(db.readMergeHeads().size(), 1);
+		assertEquals(db.readMergeHeads().get(0), ObjectId.fromString(sampleId));
+	}
+
+	public void testReadWriteMergeMsg() throws IOException {
+		assertEquals(db.readMergeCommitMsg(), null);
+		assertFalse(new File(db.getDirectory(), "MERGE_MSG").exists());
+		db.writeMergeCommitMsg(mergeMsg);
+		assertEquals(db.readMergeCommitMsg(), mergeMsg);
+		assertEquals(read(new File(db.getDirectory(), "MERGE_MSG")), mergeMsg);
+		db.writeMergeCommitMsg(null);
+		assertEquals(db.readMergeCommitMsg(), null);
+		assertFalse(new File(db.getDirectory(), "MERGE_MSG").exists());
+		FileOutputStream fos = new FileOutputStream(new File(db.getDirectory(),
+				Constants.MERGE_MSG));
+		try {
+			fos.write(mergeMsg.getBytes(Constants.CHARACTER_ENCODING));
+		} finally {
+			fos.close();
+		}
+		assertEquals(db.readMergeCommitMsg(), mergeMsg);
+	}
+
+}

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

@@ -46,8 +46,10 @@
 
 package org.eclipse.jgit.lib;
 
+import java.io.BufferedOutputStream;
 import java.io.File;
 import java.io.FileNotFoundException;
+import java.io.FileOutputStream;
 import java.io.IOException;
 import java.util.Collections;
 import java.util.HashMap;
@@ -1164,7 +1166,7 @@ public abstract class Repository {
 
 		File mergeMsgFile = new File(getDirectory(), Constants.MERGE_MSG);
 		try {
-			return new String(IO.readFully(mergeMsgFile));
+			return RawParseUtils.decode(IO.readFully(mergeMsgFile));
 		} catch (FileNotFoundException e) {
 			// MERGE_MSG file has disappeared in the meantime
 			// ignore it
@@ -1172,6 +1174,32 @@ public abstract class Repository {
 		}
 	}
 
+	/**
+	 * Write new content to the file $GIT_DIR/MERGE_MSG. In this file operations
+	 * triggering a merge will store a template for the commit message of the
+	 * merge commit. If <code>null</code> is specified as message the file will
+	 * be deleted
+	 *
+	 * @param msg
+	 *            the message which should be written or <code>null</code> to
+	 *            delete the file
+	 *
+	 * @throws IOException
+	 */
+	public void writeMergeCommitMsg(String msg) throws IOException {
+		File mergeMsgFile = new File(gitDir, Constants.MERGE_MSG);
+		if (msg != null) {
+			FileOutputStream fos = new FileOutputStream(mergeMsgFile);
+			try {
+				fos.write(msg.getBytes(Constants.CHARACTER_ENCODING));
+			} finally {
+				fos.close();
+			}
+		} else {
+			mergeMsgFile.delete();
+		}
+	}
+
 	/**
 	 * Return the information stored in the file $GIT_DIR/MERGE_HEAD. In this
 	 * file operations triggering a merge will store the IDs of all heads which
@@ -1194,11 +1222,11 @@ public abstract class Repository {
 		try {
 			raw = IO.readFully(mergeHeadFile);
 		} catch (FileNotFoundException notFound) {
-			return new LinkedList<ObjectId>();
+			return null;
 		}
 
 		if (raw.length == 0)
-			throw new IOException("MERGE_HEAD file empty: " + mergeHeadFile);
+			return null;
 
 		LinkedList<ObjectId> heads = new LinkedList<ObjectId>();
 		for (int p = 0; p < raw.length;) {
@@ -1208,4 +1236,33 @@ public abstract class Repository {
 		}
 		return heads;
 	}
+
+	/**
+	 * Write new merge-heads into $GIT_DIR/MERGE_HEAD. In this file operations
+	 * triggering a merge will store the IDs of all heads which should be merged
+	 * together with HEAD. If <code>null</code> is specified as list of commits
+	 * the file will be deleted
+	 *
+	 * @param heads
+	 *            a list of {@link Commit}s which IDs should be written to
+	 *            $GIT_DIR/MERGE_HEAD or <code>null</code> to delete the file
+	 * @throws IOException
+	 */
+	public void writeMergeHeads(List<ObjectId> heads) throws IOException {
+		File mergeHeadFile = new File(gitDir, Constants.MERGE_HEAD);
+		if (heads != null) {
+			BufferedOutputStream bos = new BufferedOutputStream(
+					new FileOutputStream(mergeHeadFile));
+			try {
+				for (ObjectId id : heads) {
+					id.copyTo(bos);
+					bos.write('\n');
+				}
+			} finally {
+				bos.close();
+			}
+		} else {
+			mergeHeadFile.delete();
+		}
+	}
 }