Refactored pre-commit hook to make it less invasive.

Hooks are now obtained via a convenient API like git commands, and
callers don't have to check for their existence.
The pre-commit hook has been updated accordingly.

Change-Id: I3383ffb10e2f3b588d7367b9139b606ec7f62758
Signed-off-by: Laurent Delaigue <laurent.delaigue@obeo.fr>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

17 files changed, 435 insertions, 238 deletions

diff --git a/org.eclipse.jgit.java7.test/META-INF/MANIFEST.MF b/org.eclipse.jgit.java7.test/META-INF/MANIFEST.MF
index a1b2782cb5..a160c8c49f 100644
--- a/org.eclipse.jgit.java7.test/META-INF/MANIFEST.MF
+++ b/org.eclipse.jgit.java7.test/META-INF/MANIFEST.MF
@@ -9,6 +9,7 @@ Import-Package: org.eclipse.jgit.api;version="[4.0.0,4.1.0)",
  org.eclipse.jgit.api.errors;version="[4.0.0,4.1.0)",
  org.eclipse.jgit.diff;version="[4.0.0,4.1.0)",
  org.eclipse.jgit.dircache;version="[4.0.0,4.1.0)",
+ org.eclipse.jgit.hooks;version="[4.0.0,4.1.0)",
  org.eclipse.jgit.internal.storage.file;version="4.0.0",
  org.eclipse.jgit.junit;version="[4.0.0,4.1.0)",
  org.eclipse.jgit.lib;version="[4.0.0,4.1.0)",
diff --git a/org.eclipse.jgit.java7.test/src/org/eclipse/jgit/util/HookTest.java b/org.eclipse.jgit.java7.test/src/org/eclipse/jgit/util/HookTest.java
index 96550889c8..0324efca6a 100644
--- a/org.eclipse.jgit.java7.test/src/org/eclipse/jgit/util/HookTest.java
+++ b/org.eclipse.jgit.java7.test/src/org/eclipse/jgit/util/HookTest.java
@@ -52,7 +52,8 @@ import java.io.IOException;
 import java.io.PrintStream;
 
 import org.eclipse.jgit.api.Git;
-import org.eclipse.jgit.api.errors.RejectCommitException;
+import org.eclipse.jgit.api.errors.AbortedByHookException;
+import org.eclipse.jgit.hooks.PreCommitHook;
 import org.eclipse.jgit.junit.JGitTestUtil;
 import org.eclipse.jgit.junit.RepositoryTestCase;
 import org.junit.Assume;
@@ -64,25 +65,25 @@ public class HookTest extends RepositoryTestCase {
 	public void testFindHook() throws Exception {
 		assumeSupportedPlatform();
 
-		Hook h = Hook.PRE_COMMIT;
-		assertNull("no hook should be installed", FS.DETECTED.findHook(db, h));
-		File hookFile = writeHookFile(h.getName(),
+		assertNull("no hook should be installed",
+				FS.DETECTED.findHook(db, PreCommitHook.NAME));
+		File hookFile = writeHookFile(PreCommitHook.NAME,
 				"#!/bin/bash\necho \"test $1 $2\"");
-		assertEquals("exected to find pre-commit hook", hookFile,
-				FS.DETECTED.findHook(db, h));
+		assertEquals("expected to find pre-commit hook", hookFile,
+				FS.DETECTED.findHook(db, PreCommitHook.NAME));
 	}
 
 	@Test
 	public void testRunHook() throws Exception {
 		assumeSupportedPlatform();
 
-		Hook h = Hook.PRE_COMMIT;
-		writeHookFile(
-				h.getName(),
+		writeHookFile(PreCommitHook.NAME,
 				"#!/bin/sh\necho \"test $1 $2\"\nread INPUT\necho $INPUT\necho 1>&2 \"stderr\"");
 		ByteArrayOutputStream out = new ByteArrayOutputStream();
 		ByteArrayOutputStream err = new ByteArrayOutputStream();
-		ProcessResult res = FS.DETECTED.runIfPresent(db, h, new String[] {
+		ProcessResult res = FS.DETECTED.runHookIfPresent(db,
+				PreCommitHook.NAME,
+				new String[] {
 				"arg1", "arg2" },
 				new PrintStream(out), new PrintStream(err), "stdin");
 		assertEquals("unexpected hook output", "test arg1 arg2\nstdin\n",
@@ -95,11 +96,10 @@ public class HookTest extends RepositoryTestCase {
 	}
 
 	@Test
-	public void testPreCommitHook() throws Exception {
+	public void testFailedPreCommitHookBlockCommit() throws Exception {
 		assumeSupportedPlatform();
 
-		Hook h = Hook.PRE_COMMIT;
-		writeHookFile(h.getName(),
+		writeHookFile(PreCommitHook.NAME,
 				"#!/bin/sh\necho \"test\"\n\necho 1>&2 \"stderr\"\nexit 1");
 		Git git = Git.wrap(db);
 		String path = "a.txt";
@@ -110,14 +110,12 @@ public class HookTest extends RepositoryTestCase {
 			git.commit().setMessage("commit")
 					.setHookOutputStream(new PrintStream(out)).call();
 			fail("expected pre-commit hook to abort commit");
-		} catch (RejectCommitException e) {
+		} catch (AbortedByHookException e) {
 			assertEquals("unexpected error message from pre-commit hook",
-					"Commit rejected by \"pre-commit\" hook.\nstderr\n",
+					"Rejected by \"pre-commit\" hook.\nstderr\n",
 					e.getMessage());
 			assertEquals("unexpected output from pre-commit hook", "test\n",
 					out.toString());
-		} catch (Throwable e) {
-			fail("unexpected exception thrown by pre-commit hook: " + e);
 		}
 	}
 
diff --git a/org.eclipse.jgit.java7/src/org/eclipse/jgit/util/FS_POSIX_Java7.java b/org.eclipse.jgit.java7/src/org/eclipse/jgit/util/FS_POSIX_Java7.java
index 300cf93bc8..118e166a29 100644
--- a/org.eclipse.jgit.java7/src/org/eclipse/jgit/util/FS_POSIX_Java7.java
+++ b/org.eclipse.jgit.java7/src/org/eclipse/jgit/util/FS_POSIX_Java7.java
@@ -352,10 +352,10 @@ public class FS_POSIX_Java7 extends FS_POSIX {
 	 * @since 3.7
 	 */
 	@Override
-	public File findHook(Repository repository, Hook hook) {
+	public File findHook(Repository repository, String hookName) {
 		final File gitdir = repository.getDirectory();
 		final Path hookPath = gitdir.toPath().resolve(Constants.HOOKS)
-				.resolve(hook.getName());
+				.resolve(hookName);
 		if (Files.isExecutable(hookPath))
 			return hookPath.toFile();
 		return null;
diff --git a/org.eclipse.jgit.java7/src/org/eclipse/jgit/util/FS_Win32_Java7Cygwin.java b/org.eclipse.jgit.java7/src/org/eclipse/jgit/util/FS_Win32_Java7Cygwin.java
index b6e5d93885..4c371de9d0 100644
--- a/org.eclipse.jgit.java7/src/org/eclipse/jgit/util/FS_Win32_Java7Cygwin.java
+++ b/org.eclipse.jgit.java7/src/org/eclipse/jgit/util/FS_Win32_Java7Cygwin.java
@@ -145,10 +145,10 @@ public class FS_Win32_Java7Cygwin extends FS_Win32_Cygwin {
 	 * @since 3.7
 	 */
 	@Override
-	public File findHook(Repository repository, Hook hook) {
+	public File findHook(Repository repository, String hookName) {
 		final File gitdir = repository.getDirectory();
 		final Path hookPath = gitdir.toPath().resolve(Constants.HOOKS)
-				.resolve(hook.getName());
+				.resolve(hookName);
 		if (Files.isExecutable(hookPath))
 			return hookPath.toFile();
 		return null;
diff --git a/org.eclipse.jgit/META-INF/MANIFEST.MF b/org.eclipse.jgit/META-INF/MANIFEST.MF
index b403052a50..42c48a17bf 100644
--- a/org.eclipse.jgit/META-INF/MANIFEST.MF
+++ b/org.eclipse.jgit/META-INF/MANIFEST.MF
@@ -53,6 +53,7 @@ Export-Package: org.eclipse.jgit.api;version="4.0.0";
    org.eclipse.jgit.lib,
    org.eclipse.jgit.revwalk",
  org.eclipse.jgit.gitrepo.internal;version="4.0.0";x-internal:=true,
+ org.eclipse.jgit.hooks;version="4.0.0",
  org.eclipse.jgit.ignore;version="4.0.0",
  org.eclipse.jgit.ignore.internal;version="4.0.0";x-friends:="org.eclipse.jgit.test",
  org.eclipse.jgit.internal;version="4.0.0";x-friends:="org.eclipse.jgit.test,org.eclipse.jgit.http.test",
diff --git a/org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties b/org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties
index 109027d936..a003b02ccd 100644
--- a/org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties
+++ b/org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties
@@ -99,12 +99,12 @@ checkoutUnexpectedResult=Checkout returned unexpected result {0}
 classCastNotA=Not a {0}
 cloneNonEmptyDirectory=Destination path "{0}" already exists and is not an empty directory
 collisionOn=Collision on {0}
+commandRejectedByHook=Rejected by "{0}" hook.\n{1}
 commandWasCalledInTheWrongState=Command {0} was called in the wrong state
 commitAlreadyExists=exists {0}
 commitMessageNotSpecified=commit message not specified
 commitOnRepoWithoutHEADCurrentlyNotSupported=Commit on repo without HEAD currently not supported
 commitAmendOnInitialNotPossible=Amending is not possible on initial commit.
-commitRejectedByHook=Commit rejected by "{0}" hook.\n{1}
 compressingObjects=Compressing objects
 connectionFailed=connection failed
 connectionTimeOut=Connection time out: {0}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/api/CommitCommand.java b/org.eclipse.jgit/src/org/eclipse/jgit/api/CommitCommand.java
index 93400aa4d1..b5c726eed0 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/api/CommitCommand.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/api/CommitCommand.java
@@ -42,7 +42,6 @@
  */
 package org.eclipse.jgit.api;
 
-import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.PrintStream;
@@ -52,13 +51,13 @@ import java.util.Collections;
 import java.util.LinkedList;
 import java.util.List;
 
+import org.eclipse.jgit.api.errors.AbortedByHookException;
 import org.eclipse.jgit.api.errors.ConcurrentRefUpdateException;
 import org.eclipse.jgit.api.errors.GitAPIException;
 import org.eclipse.jgit.api.errors.JGitInternalException;
 import org.eclipse.jgit.api.errors.NoFilepatternException;
 import org.eclipse.jgit.api.errors.NoHeadException;
 import org.eclipse.jgit.api.errors.NoMessageException;
-import org.eclipse.jgit.api.errors.RejectCommitException;
 import org.eclipse.jgit.api.errors.UnmergedPathsException;
 import org.eclipse.jgit.api.errors.WrongRepositoryStateException;
 import org.eclipse.jgit.dircache.DirCache;
@@ -67,6 +66,7 @@ import org.eclipse.jgit.dircache.DirCacheBuilder;
 import org.eclipse.jgit.dircache.DirCacheEntry;
 import org.eclipse.jgit.dircache.DirCacheIterator;
 import org.eclipse.jgit.errors.UnmergedPathException;
+import org.eclipse.jgit.hooks.Hooks;
 import org.eclipse.jgit.internal.JGitText;
 import org.eclipse.jgit.lib.CommitBuilder;
 import org.eclipse.jgit.lib.Constants;
@@ -87,9 +87,6 @@ import org.eclipse.jgit.treewalk.CanonicalTreeParser;
 import org.eclipse.jgit.treewalk.FileTreeIterator;
 import org.eclipse.jgit.treewalk.TreeWalk;
 import org.eclipse.jgit.util.ChangeIdUtil;
-import org.eclipse.jgit.util.FS;
-import org.eclipse.jgit.util.Hook;
-import org.eclipse.jgit.util.ProcessResult;
 
 /**
  * A class used to execute a {@code Commit} command. It has setters for all
@@ -126,8 +123,7 @@ public class CommitCommand extends GitCommand<RevCommit> {
 	private String reflogComment;
 
 	/**
-	 * Setting this option bypasses the {@link Hook#PRE_COMMIT pre-commit} and
-	 * {@link Hook#COMMIT_MSG commit-msg} hooks.
+	 * Setting this option bypasses the pre-commit and commit-msg hooks.
 	 */
 	private boolean noVerify;
 
@@ -138,7 +134,6 @@ public class CommitCommand extends GitCommand<RevCommit> {
 	 */
 	protected CommitCommand(Repository repo) {
 		super(repo);
-		hookOutRedirect = System.out;
 	}
 
 	/**
@@ -159,14 +154,14 @@ public class CommitCommand extends GitCommand<RevCommit> {
 	 *             else
 	 * @throws WrongRepositoryStateException
 	 *             when repository is not in the right state for committing
-	 * @throws RejectCommitException
+	 * @throws AbortedByHookException
 	 *             if there are either pre-commit or commit-msg hooks present in
-	 *             the repository and at least one of them rejects the commit.
+	 *             the repository and one of them rejects the commit.
 	 */
 	public RevCommit call() throws GitAPIException, NoHeadException,
 			NoMessageException, UnmergedPathsException,
 			ConcurrentRefUpdateException, WrongRepositoryStateException,
-			RejectCommitException {
+			AbortedByHookException {
 		checkCallable();
 		Collections.sort(only);
 
@@ -180,19 +175,7 @@ public class CommitCommand extends GitCommand<RevCommit> {
 						state.name()));
 
 			if (!noVerify) {
-				final ByteArrayOutputStream errorByteArray = new ByteArrayOutputStream();
-				final PrintStream hookErrRedirect = new PrintStream(
-						errorByteArray);
-				ProcessResult preCommitHookResult = FS.DETECTED.runIfPresent(
-						repo, Hook.PRE_COMMIT, new String[0], hookOutRedirect,
-						hookErrRedirect, null);
-				if (preCommitHookResult.getStatus() == ProcessResult.Status.OK
-						&& preCommitHookResult.getExitCode() != 0) {
-					String errorMessage = MessageFormat.format(
-							JGitText.get().commitRejectedByHook, Hook.PRE_COMMIT.getName(),
-							errorByteArray.toString());
-					throw new RejectCommitException(errorMessage);
-				}
+				Hooks.preCommit(repo, hookOutRedirect).call();
 			}
 
 			processOptions(state, rw);
@@ -771,9 +754,9 @@ public class CommitCommand extends GitCommand<RevCommit> {
 	/**
 	 * Sets the {@link #noVerify} option on this commit command.
 	 * <p>
-	 * Both the {@link Hook#PRE_COMMIT pre-commit} and {@link Hook#COMMIT_MSG
-	 * commit-msg} hooks can block a commit by their return value; setting this
-	 * option to <code>true</code> will bypass these two hooks.
+	 * Both the pre-commit and commit-msg hooks can block a commit by their
+	 * return value; setting this option to <code>true</code> will bypass these
+	 * two hooks.
 	 * </p>
 	 *
 	 * @param noVerify
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/api/errors/AbortedByHookException.java b/org.eclipse.jgit/src/org/eclipse/jgit/api/errors/AbortedByHookException.java
new file mode 100755
index 0000000000..995611ef0a
--- /dev/null
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/api/errors/AbortedByHookException.java
@@ -0,0 +1,104 @@
+/*
+ * 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.api.errors;
+
+import java.text.MessageFormat;
+
+import org.eclipse.jgit.internal.JGitText;
+
+/**
+ * Exception thrown when a hook returns a process result with a value different
+ * from 0. It is up to the caller to decide whether this should block execution
+ * or not.
+ *
+ * @since 4.0
+ */
+public class AbortedByHookException extends GitAPIException {
+	private static final long serialVersionUID = 1L;
+
+	/**
+	 * The hook that caused this exception.
+	 */
+	private final String hookName;
+
+	/**
+	 * The process result.
+	 */
+	private final int returnCode;
+
+	/**
+	 * @param message
+	 *            The error details.
+	 * @param hookName
+	 *            The name of the hook that interrupted the command, must not be
+	 *            null.
+	 * @param returnCode
+	 *            The return code of the hook process that has been run.
+	 */
+	public AbortedByHookException(String message, String hookName,
+			int returnCode) {
+		super(message);
+		this.hookName = hookName;
+		this.returnCode = returnCode;
+	}
+
+	/**
+	 * @return the type of the hook that interrupted the git command.
+	 */
+	public String getHookName() {
+		return hookName;
+	}
+
+	/**
+	 * @return the hook process result.
+	 */
+	public int getReturnCode() {
+		return returnCode;
+	}
+
+	@Override
+	public String getMessage() {
+		return MessageFormat.format(JGitText.get().commandRejectedByHook,
+				hookName, super.getMessage());
+	}
+}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/hooks/GitHook.java b/org.eclipse.jgit/src/org/eclipse/jgit/hooks/GitHook.java
new file mode 100644
index 0000000000..ad2eeb0205
--- /dev/null
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/hooks/GitHook.java
@@ -0,0 +1,159 @@
+/*
+ * 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.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.PrintStream;
+import java.util.concurrent.Callable;
+
+import org.eclipse.jgit.api.errors.AbortedByHookException;
+import org.eclipse.jgit.lib.Repository;
+import org.eclipse.jgit.util.FS;
+import org.eclipse.jgit.util.ProcessResult;
+
+/**
+ * Git can fire off custom scripts when certain important actions occur. These
+ * custom scripts are called "hooks". There are two groups of hooks: client-side
+ * (that run on local operations such as committing and merging), and
+ * server-side (that run on network operations such as receiving pushed
+ * commits). This is the abstract super-class of the different hook
+ * implementations in JGit.
+ *
+ * @param <T>
+ *            the return type which is expected from {@link #call()}
+ * @see <a href="http://git-scm.com/book/en/v2/Customizing-Git-Git-Hooks">Git
+ *      Hooks on the git-scm official site</a>
+ * @since 4.0
+ */
+abstract class GitHook<T> implements Callable<T> {
+
+	private final Repository repo;
+
+	/**
+	 * The output stream to be used by the hook.
+	 */
+	protected final PrintStream outputStream;
+
+	/**
+	 * @param repo
+	 * @param outputStream
+	 *            The output stream the hook must use. {@code null} is allowed,
+	 *            in which case the hook will use {@code System.out}.
+	 */
+	protected GitHook(Repository repo, PrintStream outputStream) {
+		this.repo = repo;
+		this.outputStream = outputStream;
+	}
+
+	/**
+	 * Run the hook.
+	 *
+	 * @throws IOException
+	 *             if IO goes wrong.
+	 * @throws AbortedByHookException
+	 *             If the hook has been run and a returned an exit code
+	 *             different from zero.
+	 */
+	public abstract T call() throws IOException, AbortedByHookException;
+
+	/**
+	 * @return The name of the hook, which must not be {@code null}.
+	 */
+	public abstract String getHookName();
+
+	/**
+	 * @return The repository.
+	 */
+	protected Repository getRepository() {
+		return repo;
+	}
+
+	/**
+	 * Override this method when needed to provide relevant parameters to the
+	 * underlying hook script. The default implementation returns an empty
+	 * array.
+	 *
+	 * @return The parameters the hook receives.
+	 */
+	protected String[] getParameters() {
+		return new String[0];
+	}
+
+	/**
+	 * Override to provide relevant arguments via stdin to the underlying hook
+	 * script. The default implementation returns {@code null}.
+	 *
+	 * @return The parameters the hook receives.
+	 */
+	protected String getStdinArgs() {
+		return null;
+	}
+
+	/**
+	 * @return The output stream the hook must use. Never {@code null},
+	 *         {@code System.out} is returned by default.
+	 */
+	protected PrintStream getOutputStream() {
+		return outputStream == null ? System.out : outputStream;
+	}
+
+	/**
+	 * Runs the hook, without performing any validity checks.
+	 *
+	 * @throws AbortedByHookException
+	 *             If the underlying hook script exited with non-zero.
+	 */
+	protected void doRun() throws AbortedByHookException {
+		final ByteArrayOutputStream errorByteArray = new ByteArrayOutputStream();
+		final PrintStream hookErrRedirect = new PrintStream(errorByteArray);
+		ProcessResult result = FS.DETECTED.runHookIfPresent(getRepository(),
+				getHookName(), getParameters(), getOutputStream(),
+				hookErrRedirect, getStdinArgs());
+		if (result.isExecutedWithError()) {
+			throw new AbortedByHookException(errorByteArray.toString(),
+					getHookName(), result.getExitCode());
+		}
+	}
+
+}
\ No newline at end of file
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/api/errors/RejectCommitException.java b/org.eclipse.jgit/src/org/eclipse/jgit/hooks/Hooks.java
index 6036a2731b..a2e4fa5609 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/api/errors/RejectCommitException.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/hooks/Hooks.java
@@ -40,22 +40,27 @@
  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
-package org.eclipse.jgit.api.errors;
+package org.eclipse.jgit.hooks;
+
+import java.io.PrintStream;
+
+import org.eclipse.jgit.lib.Repository;
 
 /**
- * Exception thrown when a commit is rejected by a hook (either
- * {@link org.eclipse.jgit.util.Hook#PRE_COMMIT pre-commit} or
- * {@link org.eclipse.jgit.util.Hook#COMMIT_MSG commit-msg}).
+ * Factory class for instantiating supported hooks.
  *
- * @since 3.7
+ * @since 4.0
  */
-public class RejectCommitException extends GitAPIException {
-	private static final long serialVersionUID = 1L;
+public class Hooks {
 
 	/**
-	 * @param message
+	 * @param repo
+	 * @param outputStream
+	 *            The output stream, or {@code null} to use {@code System.out}
+	 * @return The pre-commit hook for the given repository.
 	 */
-	public RejectCommitException(String message) {
-		super(message);
+	public static PreCommitHook preCommit(Repository repo,
+			PrintStream outputStream) {
+		return new PreCommitHook(repo, outputStream);
 	}
 }
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/hooks/PreCommitHook.java b/org.eclipse.jgit/src/org/eclipse/jgit/hooks/PreCommitHook.java
new file mode 100644
index 0000000000..1ab32e0c2b
--- /dev/null
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/hooks/PreCommitHook.java
@@ -0,0 +1,84 @@
+/*
+ * 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.IOException;
+import java.io.PrintStream;
+
+import org.eclipse.jgit.api.errors.AbortedByHookException;
+import org.eclipse.jgit.lib.Repository;
+
+/**
+ * The <code>pre-commit</code> hook implementation. This hook is run before the
+ * commit and can reject the commit.
+ *
+ * @since 4.0
+ */
+public class PreCommitHook extends GitHook<Void> {
+
+	/** The pre-commit hook name. */
+	public static final String NAME = "pre-commit"; //$NON-NLS-1$
+
+	/**
+	 * @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 PreCommitHook(Repository repo, PrintStream outputStream) {
+		super(repo, outputStream);
+	}
+
+	@Override
+	public Void call() throws IOException, AbortedByHookException {
+		doRun();
+		return null;
+	}
+
+	@Override
+	public String getHookName() {
+		return NAME;
+	}
+
+}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java
index d567a2474f..63b788f6b2 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java
@@ -158,12 +158,12 @@ public class JGitText extends TranslationBundle {
 	/***/ public String classCastNotA;
 	/***/ public String cloneNonEmptyDirectory;
 	/***/ public String collisionOn;
+	/***/ public String commandRejectedByHook;
 	/***/ public String commandWasCalledInTheWrongState;
 	/***/ public String commitAlreadyExists;
 	/***/ public String commitMessageNotSpecified;
 	/***/ public String commitOnRepoWithoutHEADCurrentlyNotSupported;
 	/***/ public String commitAmendOnInitialNotPossible;
-	/***/ public String commitRejectedByHook;
 	/***/ public String compressingObjects;
 	/***/ public String connectionFailed;
 	/***/ public String connectionTimeOut;
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/util/FS.java b/org.eclipse.jgit/src/org/eclipse/jgit/util/FS.java
index 875e12f57b..de09ad4f7c 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/util/FS.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/util/FS.java
@@ -660,8 +660,8 @@ public abstract class FS {
 	 *
 	 * @param repository
 	 *            The repository for which a hook should be run.
-	 * @param hook
-	 *            The hook to be executed.
+	 * @param hookName
+	 *            The name of the hook to be executed.
 	 * @param args
 	 *            Arguments to pass to this hook. Cannot be <code>null</code>,
 	 *            but can be an empty array.
@@ -669,11 +669,12 @@ public abstract class FS {
 	 * @throws JGitInternalException
 	 *             if we fail to run the hook somehow. Causes may include an
 	 *             interrupted process or I/O errors.
-	 * @since 3.7
+	 * @since 4.0
 	 */
-	public ProcessResult runIfPresent(Repository repository, final Hook hook,
+	public ProcessResult runHookIfPresent(Repository repository,
+			final String hookName,
 			String[] args) throws JGitInternalException {
-		return runIfPresent(repository, hook, args, System.out, System.err,
+		return runHookIfPresent(repository, hookName, args, System.out, System.err,
 				null);
 	}
 
@@ -683,8 +684,8 @@ public abstract class FS {
 	 *
 	 * @param repository
 	 *            The repository for which a hook should be run.
-	 * @param hook
-	 *            The hook to be executed.
+	 * @param hookName
+	 *            The name of the hook to be executed.
 	 * @param args
 	 *            Arguments to pass to this hook. Cannot be <code>null</code>,
 	 *            but can be an empty array.
@@ -703,9 +704,10 @@ public abstract class FS {
 	 * @throws JGitInternalException
 	 *             if we fail to run the hook somehow. Causes may include an
 	 *             interrupted process or I/O errors.
-	 * @since 3.7
+	 * @since 4.0
 	 */
-	public ProcessResult runIfPresent(Repository repository, final Hook hook,
+	public ProcessResult runHookIfPresent(Repository repository,
+			final String hookName,
 			String[] args, PrintStream outRedirect, PrintStream errRedirect,
 			String stdinArgs) throws JGitInternalException {
 		return new ProcessResult(Status.NOT_SUPPORTED);
@@ -713,13 +715,13 @@ public abstract class FS {
 
 	/**
 	 * See
-	 * {@link #runIfPresent(Repository, Hook, String[], PrintStream, PrintStream, String)}
+	 * {@link #runHookIfPresent(Repository, String, String[], PrintStream, PrintStream, String)}
 	 * . Should only be called by FS supporting shell scripts execution.
 	 *
 	 * @param repository
 	 *            The repository for which a hook should be run.
-	 * @param hook
-	 *            The hook to be executed.
+	 * @param hookName
+	 *            The name of the hook to be executed.
 	 * @param args
 	 *            Arguments to pass to this hook. Cannot be <code>null</code>,
 	 *            but can be an empty array.
@@ -738,13 +740,13 @@ public abstract class FS {
 	 * @throws JGitInternalException
 	 *             if we fail to run the hook somehow. Causes may include an
 	 *             interrupted process or I/O errors.
-	 * @since 3.7
+	 * @since 4.0
 	 */
-	protected ProcessResult internalRunIfPresent(Repository repository,
-			final Hook hook, String[] args, PrintStream outRedirect,
+	protected ProcessResult internalRunHookIfPresent(Repository repository,
+			final String hookName, String[] args, PrintStream outRedirect,
 			PrintStream errRedirect, String stdinArgs)
 			throws JGitInternalException {
-		final File hookFile = findHook(repository, hook);
+		final File hookFile = findHook(repository, hookName);
 		if (hookFile == null)
 			return new ProcessResult(Status.NOT_PRESENT);
 
@@ -764,11 +766,11 @@ public abstract class FS {
 		} catch (IOException e) {
 			throw new JGitInternalException(MessageFormat.format(
 					JGitText.get().exceptionCaughtDuringExecutionOfHook,
-					hook.getName()), e);
+					hookName), e);
 		} catch (InterruptedException e) {
 			throw new JGitInternalException(MessageFormat.format(
 					JGitText.get().exceptionHookExecutionInterrupted,
-					hook.getName()), e);
+							hookName), e);
 		}
 	}
 
@@ -778,15 +780,15 @@ public abstract class FS {
 	 *
 	 * @param repository
 	 *            The repository within which to find a hook.
-	 * @param hook
-	 *            The hook we're trying to find.
+	 * @param hookName
+	 *            The name of the hook we're trying to find.
 	 * @return The {@link File} containing this particular hook if it exists in
 	 *         the given repository, <code>null</code> otherwise.
-	 * @since 3.7
+	 * @since 4.0
 	 */
-	public File findHook(Repository repository, final Hook hook) {
+	public File findHook(Repository repository, final String hookName) {
 		final File hookFile = new File(new File(repository.getDirectory(),
-				Constants.HOOKS), hook.getName());
+				Constants.HOOKS), hookName);
 		return hookFile.isFile() ? hookFile : null;
 	}
 
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/util/FS_POSIX.java b/org.eclipse.jgit/src/org/eclipse/jgit/util/FS_POSIX.java
index ee29584239..a6984baa37 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/util/FS_POSIX.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/util/FS_POSIX.java
@@ -126,13 +126,13 @@ public abstract class FS_POSIX extends FS {
 	}
 
 	/**
-	 * @since 3.7
+	 * @since 4.0
 	 */
 	@Override
-	public ProcessResult runIfPresent(Repository repository, Hook hook,
+	public ProcessResult runHookIfPresent(Repository repository, String hookName,
 			String[] args, PrintStream outRedirect, PrintStream errRedirect,
 			String stdinArgs) throws JGitInternalException {
-		return internalRunIfPresent(repository, hook, args, outRedirect,
+		return internalRunHookIfPresent(repository, hookName, args, outRedirect,
 				errRedirect, stdinArgs);
 	}
 }
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/util/FS_Win32_Cygwin.java b/org.eclipse.jgit/src/org/eclipse/jgit/util/FS_Win32_Cygwin.java
index d0abd33275..000bdcef5c 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/util/FS_Win32_Cygwin.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/util/FS_Win32_Cygwin.java
@@ -149,13 +149,13 @@ public class FS_Win32_Cygwin extends FS_Win32 {
 	}
 
 	/**
-	 * @since 3.7
+	 * @since 4.0
 	 */
 	@Override
-	public ProcessResult runIfPresent(Repository repository, Hook hook,
+	public ProcessResult runHookIfPresent(Repository repository, String hookName,
 			String[] args, PrintStream outRedirect, PrintStream errRedirect,
 			String stdinArgs) throws JGitInternalException {
-		return internalRunIfPresent(repository, hook, args, outRedirect,
+		return internalRunHookIfPresent(repository, hookName, args, outRedirect,
 				errRedirect, stdinArgs);
 	}
 }
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/util/Hook.java b/org.eclipse.jgit/src/org/eclipse/jgit/util/Hook.java
deleted file mode 100644
index c24c9a3d0a..0000000000
--- a/org.eclipse.jgit/src/org/eclipse/jgit/util/Hook.java
+++ /dev/null
@@ -1,149 +0,0 @@
-/*
- * Copyright (C) 2014 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.util;
-
-/**
- * An enum describing the different hooks a user can implement to customize his
- * repositories.
- *
- * @since 3.7
- */
-public enum Hook {
-	/**
-	 * Literal for the "pre-commit" git hook.
-	 * <p>
-	 * This hook is invoked by git commit, and can be bypassed with the
-	 * "no-verify" option. It takes no parameter, and is invoked before
-	 * obtaining the proposed commit log message and making a commit.
-	 * </p>
-	 * <p>
-	 * A non-zero exit code from the called hook means that the commit should be
-	 * aborted.
-	 * </p>
-	 */
-	PRE_COMMIT("pre-commit"), //$NON-NLS-1$
-
-	/**
-	 * Literal for the "prepare-commit-msg" git hook.
-	 * <p>
-	 * This hook is invoked by git commit right after preparing the default
-	 * message, and before any editing possibility is displayed to the user.
-	 * </p>
-	 * <p>
-	 * A non-zero exit code from the called hook means that the commit should be
-	 * aborted.
-	 * </p>
-	 */
-	PREPARE_COMMIT_MSG("prepare-commit-msg"), //$NON-NLS-1$
-
-	/**
-	 * Literal for the "commit-msg" git hook.
-	 * <p>
-	 * This hook is invoked by git commit, and can be bypassed with the
-	 * "no-verify" option. Its single parameter is the path to the file
-	 * containing the prepared commit message (typically
-	 * "&lt;gitdir>/COMMIT-EDITMSG").
-	 * </p>
-	 * <p>
-	 * A non-zero exit code from the called hook means that the commit should be
-	 * aborted.
-	 * </p>
-	 */
-	COMMIT_MSG("commit-msg"), //$NON-NLS-1$
-
-	/**
-	 * Literal for the "post-commit" git hook.
-	 * <p>
-	 * This hook is invoked by git commit. It takes no parameter and is invoked
-	 * after a commit has been made.
-	 * </p>
-	 * <p>
-	 * The exit code of this hook has no significance.
-	 * </p>
-	 */
-	POST_COMMIT("post-commit"), //$NON-NLS-1$
-
-	/**
-	 * Literal for the "post-rewrite" git hook.
-	 * <p>
-	 * This hook is invoked after commands that rewrite commits (currently, only
-	 * "git rebase" and "git commit --amend"). It a single argument denoting the
-	 * source of the call (one of <code>rebase</code> or <code>amend</code>). It
-	 * then accepts a list of rewritten commits through stdin, in the form
-	 * <code>&lt;old SHA-1> &lt;new SHA-1>LF</code>.
-	 * </p>
-	 * <p>
-	 * The exit code of this hook has no significance.
-	 * </p>
-	 */
-	POST_REWRITE("post-rewrite"), //$NON-NLS-1$
-
-	/**
-	 * Literal for the "pre-rebase" git hook.
-	 * <p>
-	 * </p>
-	 * This hook is invoked right before the rebase operation runs. It accepts
-	 * up to two parameters, the first being the upstream from which the branch
-	 * to rebase has been forked. If the tip of the series of commits to rebase
-	 * is HEAD, the other parameter is unset. Otherwise, that tip is passed as
-	 * the second parameter of the script.
-	 * <p>
-	 * A non-zero exit code from the called hook means that the rebase should be
-	 * aborted.
-	 * </p>
-	 */
-	PRE_REBASE("pre-rebase"); //$NON-NLS-1$
-
-	private final String name;
-
-	private Hook(String name) {
-		this.name = name;
-	}
-
-	/**
-	 * @return The name of this hook.
-	 */
-	public String getName() {
-		return name;
-	}
-}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/util/ProcessResult.java b/org.eclipse.jgit/src/org/eclipse/jgit/util/ProcessResult.java
index f56bb1577e..77c9608c79 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/util/ProcessResult.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/util/ProcessResult.java
@@ -109,4 +109,13 @@ public class ProcessResult {
 	public Status getStatus() {
 		return status;
 	}
+
+	/**
+	 * @return <code>true</code> if the execution occurred and resulted in a
+	 *         return code different from 0, <code>false</code> otherwise.
+	 * @since 4.0
+	 */
+	public boolean isExecutedWithError() {
+		return getStatus() == ProcessResult.Status.OK && getExitCode() != 0;
+	}
 }