Support for the commit-msg hook.

This hook uses the file .git/COMMIT_EDITMSG to receive and potentially
modify the commit message.

Change-Id: Ibe2faadfb5d3932a5a3da2252d8156c4c04856c7
Signed-off-by: Laurent Delaigue <laurent.delaigue@obeo.fr>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit.java7.test/src/org/eclipse/jgit/util/HookTest.java

@@ -53,9 +53,11 @@ import java.io.PrintStream;
 
 import org.eclipse.jgit.api.Git;
 import org.eclipse.jgit.api.errors.AbortedByHookException;
+import org.eclipse.jgit.hooks.CommitMsgHook;
 import org.eclipse.jgit.hooks.PreCommitHook;
 import org.eclipse.jgit.junit.JGitTestUtil;
 import org.eclipse.jgit.junit.RepositoryTestCase;
+import org.eclipse.jgit.revwalk.RevCommit;
 import org.junit.Assume;
 import org.junit.Test;
 
@@ -73,6 +75,62 @@ public class HookTest extends RepositoryTestCase {
 				FS.DETECTED.findHook(db, PreCommitHook.NAME));
 	}
 
+	@Test
+	public void testFailedCommitMsgHookBlocksCommit() throws Exception {
+		assumeSupportedPlatform();
+
+		writeHookFile(CommitMsgHook.NAME,
+				"#!/bin/sh\necho \"test\"\n\necho 1>&2 \"stderr\"\nexit 1");
+		Git git = Git.wrap(db);
+		String path = "a.txt";
+		writeTrashFile(path, "content");
+		git.add().addFilepattern(path).call();
+		ByteArrayOutputStream out = new ByteArrayOutputStream();
+		try {
+			git.commit().setMessage("commit")
+					.setHookOutputStream(new PrintStream(out)).call();
+			fail("expected commit-msg hook to abort commit");
+		} catch (AbortedByHookException e) {
+			assertEquals("unexpected error message from commit-msg hook",
+					"Rejected by \"commit-msg\" hook.\nstderr\n",
+					e.getMessage());
+			assertEquals("unexpected output from commit-msg hook", "test\n",
+					out.toString());
+		}
+	}
+
+	@Test
+	public void testCommitMsgHookReceivesCorrectParameter() throws Exception {
+		assumeSupportedPlatform();
+
+		writeHookFile(CommitMsgHook.NAME,
+				"#!/bin/sh\necho $1\n\necho 1>&2 \"stderr\"\nexit 0");
+		Git git = Git.wrap(db);
+		String path = "a.txt";
+		writeTrashFile(path, "content");
+		git.add().addFilepattern(path).call();
+		ByteArrayOutputStream out = new ByteArrayOutputStream();
+		git.commit().setMessage("commit")
+				.setHookOutputStream(new PrintStream(out)).call();
+		assertEquals(".git/COMMIT_EDITMSG\n", out.toString("UTF-8"));
+	}
+
+	@Test
+	public void testCommitMsgHookCanModifyCommitMessage() throws Exception {
+		assumeSupportedPlatform();
+
+		writeHookFile(CommitMsgHook.NAME,
+				"#!/bin/sh\necho \"new message\" > $1\nexit 0");
+		Git git = Git.wrap(db);
+		String path = "a.txt";
+		writeTrashFile(path, "content");
+		git.add().addFilepattern(path).call();
+		ByteArrayOutputStream out = new ByteArrayOutputStream();
+		RevCommit revCommit = git.commit().setMessage("commit")
+				.setHookOutputStream(new PrintStream(out)).call();
+		assertEquals("new message\n", revCommit.getFullMessage());
+	}
+
 	@Test
 	public void testRunHook() throws Exception {
 		assumeSupportedPlatform();

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

@@ -214,6 +214,11 @@ public class CommitCommand extends GitCommand<RevCommit> {
 					parents.add(0, headId);
 				}
 
+			if (!noVerify) {
+				message = Hooks.commitMsg(repo, hookOutRedirect)
+						.setCommitMessage(message).call();
+			}
+
 			// lock the index
 			DirCache index = repo.lockDirCache();
 			try {

org.eclipse.jgit/src/org/eclipse/jgit/hooks/CommitMsgHook.java

@@ -0,0 +1,146 @@
+/*
+ * Copyright (C) 2015 Obeo.
+ * 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.hooks;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.PrintStream;
+
+import org.eclipse.jgit.api.errors.AbortedByHookException;
+import org.eclipse.jgit.lib.Constants;
+import org.eclipse.jgit.lib.Repository;
+
+/**
+ * The <code>commit-msg</code> hook implementation. This hook is run before the
+ * commit and can reject the commit. It passes one argument to the hook script,
+ * which is the path to the COMMIT_MSG file, relative to the repository
+ * workTree.
+ *
+ * @since 4.0
+ */
+public class CommitMsgHook extends GitHook<String> {
+
+	/**
+	 * Constant indicating the name of the commit-smg hook.
+	 */
+	public static final String NAME = "commit-msg"; //$NON-NLS-1$
+
+	/**
+	 * The commit message.
+	 */
+	private String commitMessage;
+
+	/**
+	 * @param repo
+	 *            The repository
+	 * @param outputStream
+	 *            The output stream the hook must use. {@code null} is allowed,
+	 *            in which case the hook will use {@code System.out}.
+	 */
+	protected CommitMsgHook(Repository repo, PrintStream outputStream) {
+		super(repo, outputStream);
+	}
+
+	@Override
+	public String call() throws IOException, AbortedByHookException {
+		if (commitMessage == null) {
+			throw new IllegalStateException();
+		}
+		if (canRun()) {
+			getRepository().writeCommitEditMsg(commitMessage);
+			doRun();
+			commitMessage = getRepository().readCommitEditMsg();
+		}
+		return commitMessage;
+	}
+
+	/**
+	 * @return {@code true} if and only if the path to the message commit file
+	 *         is not null (which would happen in a bare repository) and the
+	 *         commit message is also not null.
+	 */
+	private boolean canRun() {
+		return getCommitEditMessageFilePath() != null && commitMessage != null;
+	}
+
+	@Override
+	public String getHookName() {
+		return NAME;
+	}
+
+	/**
+	 * This hook receives one parameter, which is the path to the file holding
+	 * the current commit-msg, relative to the repository's work tree.
+	 */
+	@Override
+	protected String[] getParameters() {
+		return new String[] { getCommitEditMessageFilePath() };
+	}
+
+	/**
+	 * @return The path to the commit edit message file relative to the
+	 *         repository's work tree, or null if the repository is bare.
+	 */
+	private String getCommitEditMessageFilePath() {
+		File gitDir = getRepository().getDirectory();
+		if (gitDir == null) {
+			return null;
+		}
+		return Repository.stripWorkDir(getRepository().getWorkTree(), new File(
+				gitDir, Constants.COMMIT_EDITMSG));
+	}
+
+	/**
+	 * It is mandatory to call this method with a non-null value before actually
+	 * calling the hook.
+	 *
+	 * @param commitMessage
+	 *            The commit message before the hook has run.
+	 * @return {@code this} for convenience.
+	 */
+	public CommitMsgHook setCommitMessage(String commitMessage) {
+		this.commitMessage = commitMessage;
+		return this;
+	}
+
+}

org.eclipse.jgit/src/org/eclipse/jgit/hooks/Hooks.java

@@ -63,4 +63,15 @@ public class Hooks {
 			PrintStream outputStream) {
 		return new PreCommitHook(repo, outputStream);
 	}
+
+	/**
+	 * @param repo
+	 * @param outputStream
+	 *            The output stream, or {@code null} to use {@code System.out}
+	 * @return The commit-msg hook for the given repository.
+	 */
+	public static CommitMsgHook commitMsg(Repository repo,
+			PrintStream outputStream) {
+		return new CommitMsgHook(repo, outputStream);
+	}
 }

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

@@ -618,6 +618,14 @@ public final class Constants {
 	 */
 	public static final String ORIG_HEAD = "ORIG_HEAD";
 
+	/**
+	 * Name of the file in which git commands and hooks store and read the
+	 * message prepared for the upcoming commit.
+	 *
+	 * @since 4.0
+	 */
+	public static final String COMMIT_EDITMSG = "COMMIT_EDITMSG";
+
 	/** objectid for the empty blob */
 	public static final ObjectId EMPTY_BLOB_ID = ObjectId
 			.fromString("e69de29bb2d1d6434b8b29ae775ad8c2e48c5391");

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

@@ -1351,6 +1351,40 @@ public abstract class Repository implements AutoCloseable {
 		writeCommitMsg(mergeMsgFile, msg);
 	}
 
+	/**
+	 * Return the information stored in the file $GIT_DIR/COMMIT_EDITMSG. In
+	 * this file hooks triggered by an operation may read or modify the current
+	 * commit message.
+	 *
+	 * @return a String containing the content of the COMMIT_EDITMSG file or
+	 *         {@code null} if this file doesn't exist
+	 * @throws IOException
+	 * @throws NoWorkTreeException
+	 *             if this is bare, which implies it has no working directory.
+	 *             See {@link #isBare()}.
+	 * @since 4.0
+	 */
+	public String readCommitEditMsg() throws IOException, NoWorkTreeException {
+		return readCommitMsgFile(Constants.COMMIT_EDITMSG);
+	}
+
+	/**
+	 * Write new content to the file $GIT_DIR/COMMIT_EDITMSG. In this file hooks
+	 * triggered by an operation may read or modify the current commit message.
+	 * If {@code null} is specified as message the file will be deleted.
+	 *
+	 * @param msg
+	 *            the message which should be written or {@code null} to delete
+	 *            the file
+	 *
+	 * @throws IOException
+	 * @since 4.0
+	 */
+	public void writeCommitEditMsg(String msg) throws IOException {
+		File commiEditMsgFile = new File(gitDir, Constants.COMMIT_EDITMSG);
+		writeCommitMsg(commiEditMsgFile, msg);
+	}
+
 	/**
 	 * 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