Add a DiffFormatter which calculates a patch-id

Adds a class which can be used to calculates a SHA1 of the diff
associated with a patch, similar to git patch-id.

In this version whitespace is not ignored.

Change-Id: I421d15ea905e23df543082786786841cbe3ef10d
Signed-off-by: Stefan Lay <stefan.lay@sap.com>
Signed-off-by: Chris Aniszczyk <caniszczyk@gmail.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/diff/PatchIdDiffFormatterTest.java

@@ -0,0 +1,120 @@
+/*
+ * Copyright (C) 2011, Stefan Lay <stefan.lay@.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.diff;
+
+import static org.junit.Assert.assertEquals;
+
+import java.io.File;
+
+import org.eclipse.jgit.api.Git;
+import org.eclipse.jgit.dircache.DirCacheIterator;
+import org.eclipse.jgit.lib.RepositoryTestCase;
+import org.eclipse.jgit.treewalk.FileTreeIterator;
+import org.eclipse.jgit.treewalk.filter.PathFilter;
+import org.junit.Test;
+
+public class PatchIdDiffFormatterTest extends RepositoryTestCase {
+
+	@Test
+	public void testDiff() throws Exception {
+		write(new File(db.getDirectory().getParent(), "test.txt"), "test");
+		File folder = new File(db.getDirectory().getParent(), "folder");
+		folder.mkdir();
+		write(new File(folder, "folder.txt"), "folder");
+		Git git = new Git(db);
+		git.add().addFilepattern(".").call();
+		git.commit().setMessage("Initial commit").call();
+		write(new File(folder, "folder.txt"), "folder change");
+
+		PatchIdDiffFormatter df = new PatchIdDiffFormatter();
+		df.setRepository(db);
+		df.setPathFilter(PathFilter.create("folder"));
+		DirCacheIterator oldTree = new DirCacheIterator(db.readDirCache());
+		FileTreeIterator newTree = new FileTreeIterator(db);
+		df.format(oldTree, newTree);
+		df.flush();
+
+		assertEquals("1ff64e0f9333e9b81967c3e8d7a81362b14d5441", df
+				.getCalulatedPatchId().name());
+	}
+
+	@Test
+	public void testSameDiff() throws Exception {
+		write(new File(db.getDirectory().getParent(), "test.txt"), "test");
+		File folder = new File(db.getDirectory().getParent(), "folder");
+		folder.mkdir();
+		write(new File(folder, "folder.txt"), "\n\n\n\nfolder");
+		Git git = new Git(db);
+		git.add().addFilepattern(".").call();
+		git.commit().setMessage("Initial commit").call();
+		write(new File(folder, "folder.txt"), "\n\n\n\nfolder change");
+
+		PatchIdDiffFormatter df = new PatchIdDiffFormatter();
+		df.setRepository(db);
+		df.setPathFilter(PathFilter.create("folder"));
+		DirCacheIterator oldTree = new DirCacheIterator(db.readDirCache());
+		FileTreeIterator newTree = new FileTreeIterator(db);
+		df.format(oldTree, newTree);
+		df.flush();
+
+		assertEquals("08fca5ac531383eb1da8bf6b6f7cf44411281407", df
+				.getCalulatedPatchId().name());
+
+		write(new File(folder, "folder.txt"), "a\n\n\n\nfolder");
+		git.add().addFilepattern(".").call();
+		git.commit().setMessage("Initial commit").call();
+		write(new File(folder, "folder.txt"), "a\n\n\n\nfolder change");
+
+		df = new PatchIdDiffFormatter();
+		df.setRepository(db);
+		df.setPathFilter(PathFilter.create("folder"));
+		oldTree = new DirCacheIterator(db.readDirCache());
+		newTree = new FileTreeIterator(db);
+		df.format(oldTree, newTree);
+		df.flush();
+
+		assertEquals("08fca5ac531383eb1da8bf6b6f7cf44411281407", df
+				.getCalulatedPatchId().name());
+	}
+
+}

org.eclipse.jgit/src/org/eclipse/jgit/diff/DiffFormatter.java

@@ -1061,16 +1061,29 @@ public class DiffFormatter {
 		}
 
 		if (!ent.getOldId().equals(ent.getNewId())) {
-			o.write(encodeASCII("index " //
-					+ format(ent.getOldId()) //
-					+ ".." //
-					+ format(ent.getNewId())));
-			if (oldMode.equals(newMode)) {
-				o.write(' ');
-				newMode.copyTo(o);
-			}
-			o.write('\n');
+			formatIndexLine(o, ent);
+		}
+	}
+
+	/**
+	 * @param o
+	 *            the stream the formatter will write line data to
+	 * @param ent
+	 *            the DiffEntry to create the FileHeader for
+	 * @throws IOException
+	 *             writing to the supplied stream failed.
+	 */
+	protected void formatIndexLine(OutputStream o, DiffEntry ent)
+			throws IOException {
+		o.write(encodeASCII("index " //
+				+ format(ent.getOldId()) //
+				+ ".." //
+				+ format(ent.getNewId())));
+		if (ent.getOldMode().equals(ent.getNewMode())) {
+			o.write(' ');
+			ent.getNewMode().copyTo(o);
 		}
+		o.write('\n');
 	}
 
 	private void formatOldNewPaths(ByteArrayOutputStream o, DiffEntry ent)

org.eclipse.jgit/src/org/eclipse/jgit/diff/PatchIdDiffFormatter.java

@@ -0,0 +1,88 @@
+/*
+ * Copyright (C) 2011, Stefan Lay <stefan.lay@.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.diff;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.security.DigestOutputStream;
+import java.security.MessageDigest;
+
+import org.eclipse.jgit.lib.Constants;
+import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.util.io.NullOutputStream;
+
+/**
+ * A DiffFormatter used to calculate the patch-id of the diff.
+ */
+public class PatchIdDiffFormatter extends DiffFormatter {
+
+	private final MessageDigest digest;
+
+	/** Initialize a formatter to compute a patch id. */
+	public PatchIdDiffFormatter() {
+		super(new DigestOutputStream(NullOutputStream.INSTANCE,
+				Constants.newMessageDigest()));
+		digest = ((DigestOutputStream) getOutputStream()).getMessageDigest();
+	}
+
+	/**
+	 * Should be called after having called one of the format methods
+	 *
+	 * @return the patch id calculated for the provided diff.
+	 */
+	public ObjectId getCalulatedPatchId() {
+		return ObjectId.fromRaw(digest.digest());
+	}
+
+	@Override
+	protected void writeHunkHeader(int aStartLine, int aEndLine,
+			int bStartLine, int bEndLine) throws IOException {
+		// The hunk header is not taken into account for patch id calculation
+	}
+
+	@Override
+	protected void formatIndexLine(OutputStream o, DiffEntry ent)
+			throws IOException {
+		// The index line is not taken into account for patch id calculation
+	}
+}

org.eclipse.jgit/src/org/eclipse/jgit/util/io/NullOutputStream.java

@@ -0,0 +1,74 @@
+/*
+ * Copyright (C) 2011, Stefan Lay <stefan.lay@.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.io;
+
+import java.io.OutputStream;
+
+/**
+ * An OutputStream which ignores everything written to it.
+ */
+public class NullOutputStream extends OutputStream {
+
+	/** The canonical instance. */
+	public static final NullOutputStream INSTANCE = new NullOutputStream();
+
+	private NullOutputStream() {
+		// Do nothing, but we want to hide our constructor to prevent
+		// more than one instance from being created.
+	}
+
+	@Override
+	public void write(int b) {
+		// Discard.
+	}
+
+	@Override
+	public void write(byte[] buf) {
+		// Discard.
+	}
+
+	@Override
+	public void write(byte[] buf, int pos, int cnt) {
+		// Discard.
+	}
+}