Add support for built-in clean filters

JGit supports clean filters defined in repository configuration. The
filters are implemented as external programs filtering content by
accepting the original content (as seen in the working tree) on stdin
and which emit the filtered content on stdout. To run such a filter JGit
has to start an external process and pump data into/from this process.

This commit adds support for clean filters which are implemented
in Java and which are executed by jgit's main thread. When a filter is
defined in the configuration as
"jgit://builtin/<filterDriverName>/clean" then JGit will lookup in a
static map whether a filter is registered under this name. If found
such a filter is called to do the filtering.

The functionality in this commit requires that a program using JGit
explicitly calls the JGit API to register built-in implementations for
specific clean filters. In follow-up commits configuration parameters
will be added which trigger such registrations. Other commits will add
implementations for lfs filters.

Change-Id: I0344d3c54801c9a46e5a606c5df17e5f2e17b2be

1 files changed, 157 insertions, 0 deletions

diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/util/FilterCommandsTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/util/FilterCommandsTest.java
new file mode 100644
index 0000000000..5fb894e911
--- /dev/null
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/util/FilterCommandsTest.java
@@ -0,0 +1,157 @@
+/*
+ * Copyright (C) 2016, 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.util;
+
+import static org.junit.Assert.assertEquals;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+
+import org.eclipse.jgit.api.Git;
+import org.eclipse.jgit.api.errors.GitAPIException;
+import org.eclipse.jgit.attributes.FilterCommand;
+import org.eclipse.jgit.attributes.FilterCommandFactory;
+import org.eclipse.jgit.attributes.FilterCommandRegistry;
+import org.eclipse.jgit.junit.RepositoryTestCase;
+import org.eclipse.jgit.lib.Constants;
+import org.eclipse.jgit.lib.RefUpdate;
+import org.eclipse.jgit.lib.Repository;
+import org.eclipse.jgit.lib.StoredConfig;
+import org.eclipse.jgit.revwalk.RevCommit;
+import org.junit.Before;
+import org.junit.Test;
+
+public class FilterCommandsTest extends RepositoryTestCase {
+	private Git git;
+
+	RevCommit initialCommit;
+
+	RevCommit secondCommit;
+
+	class TestCommandFactory implements FilterCommandFactory {
+		private int prefix;
+
+		public TestCommandFactory(int prefix) {
+			this.prefix = prefix;
+		}
+
+		@Override
+		public FilterCommand create(Repository repo, InputStream in,
+				final OutputStream out) {
+			FilterCommand cmd = new FilterCommand(in, out) {
+
+				@Override
+				public int run() throws IOException {
+					int b = in.read();
+					if (b == -1) {
+						return b;
+					}
+					out.write(prefix);
+					out.write(b);
+					return 1;
+				}
+			};
+			return cmd;
+		}
+	}
+
+	@Override
+	@Before
+	public void setUp() throws Exception {
+		super.setUp();
+		git = new Git(db);
+		// commit something
+		writeTrashFile("Test.txt", "Hello world");
+		git.add().addFilepattern("Test.txt").call();
+		initialCommit = git.commit().setMessage("Initial commit").call();
+
+		// create a master branch and switch to it
+		git.branchCreate().setName("test").call();
+		RefUpdate rup = db.updateRef(Constants.HEAD);
+		rup.link("refs/heads/test");
+
+		// commit something on the test branch
+		writeTrashFile("Test.txt", "Some change");
+		git.add().addFilepattern("Test.txt").call();
+		secondCommit = git.commit().setMessage("Second commit").call();
+	}
+
+	@Test
+	public void testBuiltinCleanFilter()
+			throws IOException, GitAPIException {
+		String builtinCommandName = "jgit://builtin/test/clean";
+		FilterCommandRegistry.register(builtinCommandName,
+				new TestCommandFactory('c'));
+		StoredConfig config = git.getRepository().getConfig();
+		config.setString("filter", "test", "clean", builtinCommandName);
+		config.save();
+
+		writeTrashFile(".gitattributes", "*.txt filter=test");
+		git.add().addFilepattern(".gitattributes").call();
+		git.commit().setMessage("add filter").call();
+
+		writeTrashFile("Test.txt", "Hello again");
+		git.add().addFilepattern("Test.txt").call();
+		assertEquals(
+				"[.gitattributes, mode:100644, content:*.txt filter=test][Test.txt, mode:100644, content:cHceclclcoc cacgcacicn]",
+				indexState(CONTENT));
+
+		writeTrashFile("Test.bin", "Hello again");
+		git.add().addFilepattern("Test.bin").call();
+		assertEquals(
+				"[.gitattributes, mode:100644, content:*.txt filter=test][Test.bin, mode:100644, content:Hello again][Test.txt, mode:100644, content:cHceclclcoc cacgcacicn]",
+				indexState(CONTENT));
+
+		config.setString("filter", "test", "clean", null);
+		config.save();
+
+		git.add().addFilepattern("Test.txt").call();
+		assertEquals(
+				"[.gitattributes, mode:100644, content:*.txt filter=test][Test.bin, mode:100644, content:Hello again][Test.txt, mode:100644, content:Hello again]",
+				indexState(CONTENT));
+
+		config.setString("filter", "test", "clean", null);
+		config.save();
+	}
+}