patch, 6 partsDiff processing utilities

org.spearce.jgit.test/tst/org/spearce/jgit/util/IntListTest.java, org.spearce.jgit/src/org/spearce/jgit/util/IntList.java

diff --git a/org.spearce.jgit.test/tst/org/spearce/jgit/util/IntListTest.java b/org.spearce.jgit.test/tst/org/spearce/jgit/util/IntListTest.java
index c470d55..ce0d7af 100644
--- a/org.spearce.jgit.test/tst/org/spearce/jgit/util/IntListTest.java
+++ b/org.spearce.jgit.test/tst/org/spearce/jgit/util/IntListTest.java
@@ -144,6 +144,27 @@ public void testClear() {
 		}
 	}
 
+	public void testSet() {
+		final IntList i = new IntList();
+		i.add(1);
+		assertEquals(1, i.size());
+		assertEquals(1, i.get(0));
+		
+		i.set(0, 5);
+		assertEquals(5, i.get(0));
+		
+		try {
+			i.set(5, 5);
+			fail("accepted set of 5 beyond end of list");
+		} catch (ArrayIndexOutOfBoundsException e){
+			assertTrue(true);
+		}
+
+		i.set(1, 2);
+		assertEquals(2, i.size());
+		assertEquals(2, i.get(1));
+	}
+
 	public void testToString() {
 		final IntList i = new IntList();
 		i.add(1);
diff --git a/org.spearce.jgit/src/org/spearce/jgit/util/IntList.java b/org.spearce.jgit/src/org/spearce/jgit/util/IntList.java
index 0a84793..9d86a5c 100644
--- a/org.spearce.jgit/src/org/spearce/jgit/util/IntList.java
+++ b/org.spearce.jgit/src/org/spearce/jgit/util/IntList.java
@@ -94,6 +94,23 @@ public void add(final int n) {
 	}
 
 	/**
+	 * Assign an entry in the list.
+	 * 
+	 * @param index
+	 *            index to set, must be in the range [0, {@link #size()}).
+	 * @param n
+	 *            value to store at the position.
+	 */
+	public void set(final int index, final int n) {
+		if (count < index)
+			throw new ArrayIndexOutOfBoundsException(index);
+		else if (count == index)
+			add(n);
+		else
+			entries[index] = n;
+	}
+	
+	/**
 	 * Pad the list with entries.
 	 *
 	 * @param toIndex

org.spearce.jgit.test/tst/org/spearce/jgit/diff/EditTest.java, org.spearce.jgit/src/org/spearce/jgit/diff/Edit.java

diff --git a/org.spearce.jgit.test/tst/org/spearce/jgit/diff/EditTest.java b/org.spearce.jgit.test/tst/org/spearce/jgit/diff/EditTest.java
new file mode 100644
index 0000000..8f9b0e3
--- /dev/null
+++ b/org.spearce.jgit.test/tst/org/spearce/jgit/diff/EditTest.java
@@ -0,0 +1,139 @@
+/*
+ * Copyright (C) 2009, Google Inc.
+ *
+ * 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 Git Development Community 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.spearce.jgit.diff;
+
+import junit.framework.TestCase;
+
+public class EditTest extends TestCase {
+	public void testCreate() {
+		final Edit e = new Edit(1, 2, 3, 4);
+		assertEquals(1, e.getBeginA());
+		assertEquals(2, e.getEndA());
+		assertEquals(3, e.getBeginB());
+		assertEquals(4, e.getEndB());
+	}
+
+	public void testCreateEmpty() {
+		final Edit e = new Edit(1, 3);
+		assertEquals(1, e.getBeginA());
+		assertEquals(1, e.getEndA());
+		assertEquals(3, e.getBeginB());
+		assertEquals(3, e.getEndB());
+	}
+
+	public void testSwap() {
+		final Edit e = new Edit(1, 2, 3, 4);
+		e.swap();
+		assertEquals(3, e.getBeginA());
+		assertEquals(4, e.getEndA());
+		assertEquals(1, e.getBeginB());
+		assertEquals(2, e.getEndB());
+	}
+
+	public void testType_Insert() {
+		final Edit e = new Edit(1, 1, 1, 2);
+		assertSame(Edit.Type.INSERT, e.getType());
+	}
+
+	public void testType_Delete() {
+		final Edit e = new Edit(1, 2, 1, 1);
+		assertSame(Edit.Type.DELETE, e.getType());
+	}
+
+	public void testType_Replace() {
+		final Edit e = new Edit(1, 2, 1, 4);
+		assertSame(Edit.Type.REPLACE, e.getType());
+	}
+
+	public void testType_Empty() {
+		assertSame(Edit.Type.EMPTY, new Edit(1, 1, 2, 2).getType());
+		assertSame(Edit.Type.EMPTY, new Edit(1, 2).getType());
+	}
+
+	public void testToString() {
+		final Edit e = new Edit(1, 2, 1, 4);
+		assertEquals("REPLACE(1-2,1-4)", e.toString());
+	}
+
+	public void testEquals1() {
+		final Edit e1 = new Edit(1, 2, 3, 4);
+		final Edit e2 = new Edit(1, 2, 3, 4);
+
+		assertTrue(e1.equals(e1));
+		assertTrue(e1.equals(e2));
+		assertTrue(e2.equals(e1));
+		assertEquals(e1.hashCode(), e2.hashCode());
+		assertFalse(e1.equals(""));
+	}
+
+	public void testNotEquals1() {
+		assertFalse(new Edit(1, 2, 3, 4).equals(new Edit(0, 2, 3, 4)));
+	}
+
+	public void testNotEquals2() {
+		assertFalse(new Edit(1, 2, 3, 4).equals(new Edit(1, 0, 3, 4)));
+	}
+
+	public void testNotEquals3() {
+		assertFalse(new Edit(1, 2, 3, 4).equals(new Edit(1, 2, 0, 4)));
+	}
+
+	public void testNotEquals4() {
+		assertFalse(new Edit(1, 2, 3, 4).equals(new Edit(1, 2, 3, 0)));
+	}
+
+	public void testExtendA() {
+		final Edit e = new Edit(1, 2, 1, 1);
+
+		e.extendA();
+		assertEquals(new Edit(1, 3, 1, 1), e);
+
+		e.extendA();
+		assertEquals(new Edit(1, 4, 1, 1), e);
+	}
+
+	public void testExtendB() {
+		final Edit e = new Edit(1, 2, 1, 1);
+
+		e.extendB();
+		assertEquals(new Edit(1, 2, 1, 2), e);
+
+		e.extendB();
+		assertEquals(new Edit(1, 2, 1, 3), e);
+	}
+}
diff --git a/org.spearce.jgit/src/org/spearce/jgit/diff/Edit.java b/org.spearce.jgit/src/org/spearce/jgit/diff/Edit.java
new file mode 100644
index 0000000..460e2c4
--- /dev/null
+++ b/org.spearce.jgit/src/org/spearce/jgit/diff/Edit.java
@@ -0,0 +1,189 @@
+/*
+ * Copyright (C) 2008, Johannes E. Schindelin <johannes.schindelin@gmx.de>
+ *
+ * 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 Git Development Community 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.spearce.jgit.diff;
+
+/**
+ * A modified region detected between two versions of roughly the same content.
+ * <p>
+ * An edit covers the modified region only. It does not cover a common region.
+ * <p>
+ * Regions should be specified using 0 based notation, so add 1 to the start and
+ * end marks for line numbers in a file.
+ * <p>
+ * An edit where <code>beginA == endA && beginB < endB</code> is an insert edit,
+ * that is sequence B inserted the elements in region
+ * <code>[beginB, endB)</code> at <code>beginA</code>.
+ * <p>
+ * An edit where <code>beginA < endA && beginB == endB</code> is a delete edit,
+ * that is sequence B has removed the elements between
+ * <code>[beginA, endA)</code>.
+ * <p>
+ * An edit where <code>beginA < endA && beginB < endB</code> is a replace edit,
+ * that is sequence B has replaced the range of elements between
+ * <code>[beginA, endA)</code> with those found in <code>[beginB, endB)</code>.
+ */
+public class Edit {
+	/** Type of edit */
+	public static enum Type {
+		/** Sequence B has inserted the region. */
+		INSERT,
+
+		/** Sequence B has removed the region. */
+		DELETE,
+
+		/** Sequence B has replaced the region with different content. */
+		REPLACE,
+
+		/** Sequence A and B have zero length, describing nothing. */
+		EMPTY;
+	}
+
+	int beginA;
+
+	int endA;
+
+	int beginB;
+
+	int endB;
+
+	/**
+	 * Create a new empty edit.
+	 * 
+	 * @param as
+	 *            beginA: start and end of region in sequence A; 0 based.
+	 * @param bs
+	 *            beginB: start and end of region in sequence B; 0 based.
+	 */
+	public Edit(final int as, final int bs) {
+		this(as, as, bs, bs);
+	}
+
+	/**
+	 * Create a new edit.
+	 * 
+	 * @param as
+	 *            beginA: start of region in sequence A; 0 based.
+	 * @param ae
+	 *            endA: end of region in sequence A; must be >= as.
+	 * @param bs
+	 *            beginB: start of region in sequence B; 0 based.
+	 * @param be
+	 *            endB: end of region in sequence B; must be >= bs.
+	 */
+	public Edit(final int as, final int ae, final int bs, final int be) {
+		beginA = as;
+		endA = ae;
+
+		beginB = bs;
+		endB = be;
+	}
+
+	/** @return the type of this region */
+	public final Type getType() {
+		if (beginA == endA && beginB < endB)
+			return Type.INSERT;
+		if (beginA < endA && beginB == endB)
+			return Type.DELETE;
+		if (beginA == endA && beginB == endB)
+			return Type.EMPTY;
+		return Type.REPLACE;
+	}
+
+	/** @return start point in sequence A. */
+	public final int getBeginA() {
+		return beginA;
+	}
+
+	/** @return end point in sequence A. */
+	public final int getEndA() {
+		return endA;
+	}
+
+	/** @return start point in sequence B. */
+	public final int getBeginB() {
+		return beginB;
+	}
+
+	/** @return end point in sequence B. */
+	public final int getEndB() {
+		return endB;
+	}
+
+	/** Increase {@link #getEndA()} by 1. */
+	public void extendA() {
+		endA++;
+	}
+
+	/** Increase {@link #getEndB()} by 1. */
+	public void extendB() {
+		endB++;
+	}
+
+	/** Swap A and B, so the edit goes the other direction. */
+	public void swap() {
+		final int sBegin = beginA;
+		final int sEnd = endA;
+
+		beginA = beginB;
+		endA = endB;
+
+		beginB = sBegin;
+		endB = sEnd;
+	}
+
+	@Override
+	public int hashCode() {
+		return beginA ^ endA;
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (o instanceof Edit) {
+			final Edit e = (Edit) o;
+			return this.beginA == e.beginA && this.endA == e.endA
+					&& this.beginB == e.beginB && this.endB == e.endB;
+		}
+		return false;
+	}
+
+	@Override
+	public String toString() {
+		final Type t = getType();
+		return t + "(" + beginA + "-" + endA + "," + beginB + "-" + endB + ")";
+	}
+}

org.spearce.jgit.test/tst/org/spearce/jgit/diff/EditListTest.java, org.spearce.jgit/src/org/spearce/jgit/diff/EditList.java

diff --git a/org.spearce.jgit.test/tst/org/spearce/jgit/diff/EditListTest.java b/org.spearce.jgit.test/tst/org/spearce/jgit/diff/EditListTest.java
new file mode 100644
index 0000000..54d5007
--- /dev/null
+++ b/org.spearce.jgit.test/tst/org/spearce/jgit/diff/EditListTest.java
@@ -0,0 +1,121 @@
+/*
+ * Copyright (C) 2009, Google Inc.
+ *
+ * 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 Git Development Community 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.spearce.jgit.diff;
+
+import java.util.Iterator;
+
+import junit.framework.TestCase;
+
+public class EditListTest extends TestCase {
+	public void testEmpty() {
+		final EditList l = new EditList();
+		assertEquals(0, l.size());
+		assertTrue(l.isEmpty());
+		assertEquals("EditList[]", l.toString());
+
+		assertTrue(l.equals(l));
+		assertTrue(l.equals(new EditList()));
+		assertFalse(l.equals(""));
+		assertEquals(l.hashCode(), new EditList().hashCode());
+	}
+
+	public void testAddOne() {
+		final Edit e = new Edit(1, 2, 1, 1);
+		final EditList l = new EditList();
+		l.add(e);
+		assertEquals(1, l.size());
+		assertFalse(l.isEmpty());
+		assertSame(e, l.get(0));
+		assertSame(e, l.iterator().next());
+
+		assertTrue(l.equals(l));
+		assertFalse(l.equals(new EditList()));
+
+		final EditList l2 = new EditList();
+		l2.add(e);
+		assertTrue(l.equals(l2));
+		assertTrue(l2.equals(l));
+		assertEquals(l.hashCode(), l2.hashCode());
+	}
+
+	public void testAddTwo() {
+		final Edit e1 = new Edit(1, 2, 1, 1);
+		final Edit e2 = new Edit(8, 8, 8, 12);
+		final EditList l = new EditList();
+		l.add(e1);
+		l.add(e2);
+		assertEquals(2, l.size());
+		assertSame(e1, l.get(0));
+		assertSame(e2, l.get(1));
+
+		final Iterator<Edit> i = l.iterator();
+		assertSame(e1, i.next());
+		assertSame(e2, i.next());
+
+		assertTrue(l.equals(l));
+		assertFalse(l.equals(new EditList()));
+
+		final EditList l2 = new EditList();
+		l2.add(e1);
+		l2.add(e2);
+		assertTrue(l.equals(l2));
+		assertTrue(l2.equals(l));
+		assertEquals(l.hashCode(), l2.hashCode());
+	}
+
+	public void testSet() {
+		final Edit e1 = new Edit(1, 2, 1, 1);
+		final Edit e2 = new Edit(3, 4, 3, 3);
+		final EditList l = new EditList();
+		l.add(e1);
+		assertSame(e1, l.get(0));
+		assertSame(e1, l.set(0, e2));
+		assertSame(e2, l.get(0));
+	}
+
+	public void testRemove() {
+		final Edit e1 = new Edit(1, 2, 1, 1);
+		final Edit e2 = new Edit(8, 8, 8, 12);
+		final EditList l = new EditList();
+		l.add(e1);
+		l.add(e2);
+		l.remove(e1);
+		assertEquals(1, l.size());
+		assertSame(e2, l.get(0));
+	}
+}
diff --git a/org.spearce.jgit/src/org/spearce/jgit/diff/EditList.java b/org.spearce.jgit/src/org/spearce/jgit/diff/EditList.java
new file mode 100644
index 0000000..0ccf366
--- /dev/null
+++ b/org.spearce.jgit/src/org/spearce/jgit/diff/EditList.java
@@ -0,0 +1,93 @@
+/*
+ * Copyright (C) 2009, Google Inc.
+ *
+ * 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 Git Development Community 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.spearce.jgit.diff;
+
+import java.util.AbstractList;
+import java.util.ArrayList;
+
+/** Specialized list of {@link Edit}s in a document. */
+public class EditList extends AbstractList<Edit> {
+	private final ArrayList<Edit> container;
+
+	/** Create a new, empty edit list. */
+	public EditList() {
+		container = new ArrayList<Edit>();
+	}
+
+	@Override
+	public int size() {
+		return container.size();
+	}
+
+	@Override
+	public Edit get(final int index) {
+		return container.get(index);
+	}
+
+	@Override
+	public Edit set(final int index, final Edit element) {
+		return container.set(index, element);
+	}
+
+	@Override
+	public void add(final int index, final Edit element) {
+		container.add(index, element);
+	}
+
+	@Override
+	public Edit remove(final int index) {
+		return container.remove(index);
+	}
+
+	@Override
+	public int hashCode() {
+		return container.hashCode();
+	}
+
+	@Override
+	public boolean equals(final Object o) {
+		if (o instanceof EditList)
+			return container.equals(((EditList) o).container);
+		return false;
+	}
+
+	@Override
+	public String toString() {
+		return "EditList" + container.toString();
+	}
+}

org.spearce.jgit.test/tst/org/spearce/jgit/diff/RawTextTest.java, org.spearce.jgit/src/org/spearce/jgit/diff/RawText.java, org.spearce.jgit/src/org/spearce/jgit/diff/Sequence.java

diff --git a/org.spearce.jgit.test/tst/org/spearce/jgit/diff/RawTextTest.java b/org.spearce.jgit.test/tst/org/spearce/jgit/diff/RawTextTest.java
new file mode 100644
index 0000000..a7c621e
--- /dev/null
+++ b/org.spearce.jgit.test/tst/org/spearce/jgit/diff/RawTextTest.java
@@ -0,0 +1,93 @@
+/*
+ * Copyright (C) 2009, Google Inc.
+ *
+ * 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 Git Development Community 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.spearce.jgit.diff;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+
+import junit.framework.TestCase;
+
+import org.spearce.jgit.lib.Constants;
+import org.spearce.jgit.util.RawParseUtils;
+
+public class RawTextTest extends TestCase {
+	public void testEmpty() {
+		final RawText r = new RawText(new byte[0]);
+		assertEquals(0, r.size());
+	}
+
+	public void testEquals() {
+		final RawText a = new RawText(Constants.encodeASCII("foo-a\nfoo-b\n"));
+		final RawText b = new RawText(Constants.encodeASCII("foo-b\nfoo-c\n"));
+
+		assertEquals(2, a.size());
+		assertEquals(2, b.size());
+
+		// foo-a != foo-b
+		assertFalse(a.equals(0, b, 0));
+		assertFalse(b.equals(0, a, 0));
+
+		// foo-b == foo-b
+		assertTrue(a.equals(1, b, 0));
+		assertTrue(b.equals(0, a, 1));
+	}
+
+	public void testWriteLine1() throws IOException {
+		final RawText a = new RawText(Constants.encodeASCII("foo-a\nfoo-b\n"));
+		final ByteArrayOutputStream o = new ByteArrayOutputStream();
+		a.writeLine(o, 0);
+		final byte[] r = o.toByteArray();
+		assertEquals("foo-a", RawParseUtils.decode(r));
+	}
+
+	public void testWriteLine2() throws IOException {
+		final RawText a = new RawText(Constants.encodeASCII("foo-a\nfoo-b"));
+		final ByteArrayOutputStream o = new ByteArrayOutputStream();
+		a.writeLine(o, 1);
+		final byte[] r = o.toByteArray();
+		assertEquals("foo-b", RawParseUtils.decode(r));
+	}
+
+	public void testWriteLine3() throws IOException {
+		final RawText a = new RawText(Constants.encodeASCII("a\n\nb\n"));
+		final ByteArrayOutputStream o = new ByteArrayOutputStream();
+		a.writeLine(o, 1);
+		final byte[] r = o.toByteArray();
+		assertEquals("", RawParseUtils.decode(r));
+	}
+}
diff --git a/org.spearce.jgit/src/org/spearce/jgit/diff/RawText.java b/org.spearce.jgit/src/org/spearce/jgit/diff/RawText.java
new file mode 100644
index 0000000..1d10082
--- /dev/null
+++ b/org.spearce.jgit/src/org/spearce/jgit/diff/RawText.java
@@ -0,0 +1,172 @@
+/*
+ * Copyright (C) 2008, Johannes E. Schindelin <johannes.schindelin@gmx.de>
+ * Copyright (C) 2009, Google Inc.
+ *
+ * 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 Git Development Community 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.spearce.jgit.diff;
+
+import java.io.IOException;
+import java.io.OutputStream;
+
+import org.spearce.jgit.util.IntList;
+import org.spearce.jgit.util.RawParseUtils;
+
+/**
+ * A Sequence supporting UNIX formatted text in byte[] format.
+ * <p>
+ * Elements of the sequence are the lines of the file, as delimited by the UNIX
+ * newline character ('\n'). The file content is treated as 8 bit binary text,
+ * with no assumptions or requirements on character encoding.
+ * <p>
+ * Note that the first line of the file is element 0, as defined by the Sequence
+ * interface API. Traditionally in a text editor a patch file the first line is
+ * line number 1. Callers may need to subtract 1 prior to invoking methods if
+ * they are converting from "line number" to "element index".
+ */
+public class RawText implements Sequence {
+	/** The file content for this sequence. */
+	protected final byte[] content;
+
+	/** Map of line number to starting position within {@link #content}. */
+	protected final IntList lines;
+
+	/** Hash code for each line, for fast equality elimination. */
+	protected final IntList hashes;
+
+	/**
+	 * Create a new sequence from an existing content byte array.
+	 * <p>
+	 * The entire array (indexes 0 through length-1) is used as the content.
+	 * 
+	 * @param input
+	 *            the content array. The array is never modified, so passing
+	 *            through cached arrays is safe.
+	 */
+	public RawText(final byte[] input) {
+		content = input;
+		lines = RawParseUtils.lineMap(content, 0, content.length);
+		hashes = computeHashes();
+	}
+
+	public int size() {
+		// The line map is always 2 entries larger than the number of lines in
+		// the file. Index 0 is padded out/unused. The last index is the total
+		// length of the buffer, and acts as a sentinel.
+		//
+		return lines.size() - 2;
+	}
+
+	public boolean equals(final int i, final Sequence other, final int j) {
+		return equals(this, i + 1, (RawText) other, j + 1);
+	}
+
+	private static boolean equals(final RawText a, final int ai,
+			final RawText b, final int bi) {
+		if (a.hashes.get(ai) != b.hashes.get(bi))
+			return false;
+
+		int as = a.lines.get(ai);
+		int bs = b.lines.get(bi);
+		final int ae = a.lines.get(ai + 1);
+		final int be = b.lines.get(bi + 1);
+
+		if (ae - as != be - bs)
+			return false;
+
+		while (as < ae) {
+			if (a.content[as++] != b.content[bs++])
+				return false;
+		}
+		return true;
+	}
+
+	/**
+	 * Write a specific line to the output stream, without its trailing LF.
+	 * <p>
+	 * The specified line is copied as-is, with no character encoding
+	 * translation performed.
+	 * <p>
+	 * If the specified line ends with an LF ('\n'), the LF is <b>not</b>
+	 * copied. It is up to the caller to write the LF, if desired, between
+	 * output lines.
+	 * 
+	 * @param out
+	 *            stream to copy the line data onto.
+	 * @param i
+	 *            index of the line to extract. Note this is 0-based, so line
+	 *            number 1 is actually index 0.
+	 * @throws IOException
+	 *             the stream write operation failed.
+	 */
+	public void writeLine(final OutputStream out, final int i)
+			throws IOException {
+		final int start = lines.get(i + 1);
+		int end = lines.get(i + 2);
+		if (content[end - 1] == '\n')
+			end--;
+		out.write(content, start, end - start);
+	}
+
+	private IntList computeHashes() {
+		final IntList r = new IntList(lines.size());
+		r.add(0);
+		for (int lno = 1; lno < lines.size() - 1; lno++) {
+			final int ptr = lines.get(lno);
+			final int end = lines.get(lno + 1);
+			r.add(hashLine(content, ptr, end));
+		}
+		r.add(0);
+		return r;
+	}
+
+	/**
+	 * Compute a hash code for a single line.
+	 * 
+	 * @param raw
+	 *            the raw file content.
+	 * @param ptr
+	 *            first byte of the content line to hash.
+	 * @param end
+	 *            1 past the last byte of the content line.
+	 * @return hash code for the region <code>[ptr, end)</code> of raw.
+	 */
+	protected int hashLine(final byte[] raw, int ptr, final int end) {
+		int hash = 5381;
+		for (; ptr < end; ptr++)
+			hash = (hash << 5) ^ (raw[ptr] & 0xff);
+		return hash;
+	}
+}
\ No newline at end of file
diff --git a/org.spearce.jgit/src/org/spearce/jgit/diff/Sequence.java b/org.spearce.jgit/src/org/spearce/jgit/diff/Sequence.java
new file mode 100644
index 0000000..8e754e0
--- /dev/null
+++ b/org.spearce.jgit/src/org/spearce/jgit/diff/Sequence.java
@@ -0,0 +1,78 @@
+/*
+ * Copyright (C) 2008, Johannes E. Schindelin <johannes.schindelin@gmx.de>
+ *
+ * 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 Git Development Community 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.spearce.jgit.diff;
+
+/**
+ * Arbitrary sequence of elements with fast comparison support.
+ * <p>
+ * A sequence of elements is defined to contain elements in the index range
+ * <code>[0, {@link #size()})</code>, like a standard Java List implementation.
+ * Unlike a List, the members of the sequence are not directly obtainable, but
+ * element equality can be tested if two Sequences are the same implementation.
+ * <p>
+ * An implementation may chose to implement the equals semantic as necessary,
+ * including fuzzy matching rules such as ignoring insignificant sub-elements,
+ * e.g. ignoring whitespace differences in text.
+ * <p>
+ * Implementations of Sequence are primarily intended for use in content
+ * difference detection algorithms, to produce an {@link EditList} of
+ * {@link Edit} instances describing how two Sequence instances differ.
+ */
+public interface Sequence {
+	/** @return total number of items in the sequence. */
+	public int size();
+
+	/**
+	 * Determine if the i-th member is equal to the j-th member.
+	 * <p>
+	 * Implementations must ensure <code>equals(thisIdx,other,otherIdx)</code>
+	 * returns the same as <code>other.equals(otherIdx,this,thisIdx)</code>.
+	 * 
+	 * @param thisIdx
+	 *            index within <code>this</code> sequence; must be in the range
+	 *            <code>[ 0, this.size() )</code>.
+	 * @param other
+	 *            another sequence; must be the same implementation class, that
+	 *            is <code>this.getClass() == other.getClass()</code>.
+	 * @param otherIdx
+	 *            index within <code>other</code> sequence; must be in the range
+	 *            <code>[ 0, other.size() )</code>.
+	 * @return true if the elements are equal; false if they are not equal.
+	 */
+	public boolean equals(int thisIdx, Sequence other, int otherIdx);
+}
\ No newline at end of file

org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/patch/testEditList_Types.patch, org.spearce.jgit.test/tst/org/spearce/jgit/patch/EditListTest.java, org.spearce.jgit/src/org/spearce/jgit/patch/FileHeader.java, org.spearce.jgit/src/org/spearce/jgit/patch/HunkHeader.java

diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/patch/testEditList_Types.patch b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/patch/testEditList_Types.patch
new file mode 100644
index 0000000..e5363eb
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/patch/testEditList_Types.patch
@@ -0,0 +1,24 @@
+diff --git a/X b/X
+index a3648a1..2d44096 100644
+--- a/X
++++ b/X
+@@ -2,2 +2,3 @@ a
+ b
++c
+ d
+@@ -16,4 +17,2 @@ p
+ q
+-r
+-s
+ t
+@@ -22,4 +21,8 @@ v
+ w
+-x
+-y
++0
++1
++2
++3
++4
++5
+ z
diff --git a/org.spearce.jgit.test/tst/org/spearce/jgit/patch/EditListTest.java b/org.spearce.jgit.test/tst/org/spearce/jgit/patch/EditListTest.java
new file mode 100644
index 0000000..452f661
--- /dev/null
+++ b/org.spearce.jgit.test/tst/org/spearce/jgit/patch/EditListTest.java
@@ -0,0 +1,95 @@
+/*
+ * Copyright (C) 2009, Google Inc.
+ *
+ * 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 Git Development Community 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.spearce.jgit.patch;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+import junit.framework.TestCase;
+
+import org.spearce.jgit.diff.Edit;
+import org.spearce.jgit.diff.EditList;
+
+public class EditListTest extends TestCase {
+	public void testHunkHeader() throws IOException {
+		final Patch p = parseTestPatchFile("testGetText_BothISO88591.patch");
+		final FileHeader fh = p.getFiles().get(0);
+
+		final EditList list0 = fh.getHunks().get(0).toEditList();
+		assertEquals(1, list0.size());
+		assertEquals(new Edit(4 - 1, 5 - 1, 4 - 1, 5 - 1), list0.get(0));
+
+		final EditList list1 = fh.getHunks().get(1).toEditList();
+		assertEquals(1, list1.size());
+		assertEquals(new Edit(16 - 1, 17 - 1, 16 - 1, 17 - 1), list1.get(0));
+	}
+
+	public void testFileHeader() throws IOException {
+		final Patch p = parseTestPatchFile("testGetText_BothISO88591.patch");
+		final FileHeader fh = p.getFiles().get(0);
+		final EditList e = fh.toEditList();
+		assertEquals(2, e.size());
+		assertEquals(new Edit(4 - 1, 5 - 1, 4 - 1, 5 - 1), e.get(0));
+		assertEquals(new Edit(16 - 1, 17 - 1, 16 - 1, 17 - 1), e.get(1));
+	}
+
+	public void testTypes() throws IOException {
+		final Patch p = parseTestPatchFile("testEditList_Types.patch");
+		final FileHeader fh = p.getFiles().get(0);
+		final EditList e = fh.toEditList();
+		assertEquals(3, e.size());
+		assertEquals(new Edit(3 - 1, 3 - 1, 3 - 1, 4 - 1), e.get(0));
+		assertEquals(new Edit(17 - 1, 19 - 1, 18 - 1, 18 - 1), e.get(1));
+		assertEquals(new Edit(23 - 1, 25 - 1, 22 - 1, 28 - 1), e.get(2));
+	}
+
+	private Patch parseTestPatchFile(final String patchFile) throws IOException {
+		final InputStream in = getClass().getResourceAsStream(patchFile);
+		if (in == null) {
+			fail("No " + patchFile + " test vector");
+			return null; // Never happens
+		}
+		try {
+			final Patch p = new Patch();
+			p.parse(in);
+			return p;
+		} finally {
+			in.close();
+		}
+	}
+}
diff --git a/org.spearce.jgit/src/org/spearce/jgit/patch/FileHeader.java b/org.spearce.jgit/src/org/spearce/jgit/patch/FileHeader.java
index 7d341d8..c64f742 100644
--- a/org.spearce.jgit/src/org/spearce/jgit/patch/FileHeader.java
+++ b/org.spearce.jgit/src/org/spearce/jgit/patch/FileHeader.java
@@ -52,6 +52,7 @@
 import java.util.Collections;
 import java.util.List;
 
+import org.spearce.jgit.diff.EditList;
 import org.spearce.jgit.lib.AbbreviatedObjectId;
 import org.spearce.jgit.lib.Constants;
 import org.spearce.jgit.lib.FileMode;
@@ -423,6 +424,14 @@ public BinaryHunk getReverseBinaryHunk() {
 		return reverseBinaryHunk;
 	}
 
+	/** @return a list describing the content edits performed on this file. */
+	public EditList toEditList() {
+		final EditList r = new EditList();
+		for (final HunkHeader hunk : hunks)
+			r.addAll(hunk.toEditList());
+		return r;
+	}
+
 	/**
 	 * Parse a "diff --git" or "diff --cc" line.
 	 *
diff --git a/org.spearce.jgit/src/org/spearce/jgit/patch/HunkHeader.java b/org.spearce.jgit/src/org/spearce/jgit/patch/HunkHeader.java
index e9c55e3..af128ab 100644
--- a/org.spearce.jgit/src/org/spearce/jgit/patch/HunkHeader.java
+++ b/org.spearce.jgit/src/org/spearce/jgit/patch/HunkHeader.java
@@ -44,6 +44,8 @@
 import java.io.IOException;
 import java.io.OutputStream;
 
+import org.spearce.jgit.diff.Edit;
+import org.spearce.jgit.diff.EditList;
 import org.spearce.jgit.lib.AbbreviatedObjectId;
 import org.spearce.jgit.util.MutableInteger;
 
@@ -161,6 +163,52 @@ public int getLinesContext() {
 		return nContext;
 	}
 
+	/** @return a list describing the content edits performed within the hunk. */
+	public EditList toEditList() {
+		final EditList r = new EditList();
+		final byte[] buf = file.buf;
+		int c = nextLF(buf, startOffset);
+		int oLine = old.startLine;
+		int nLine = newStartLine;
+		Edit in = null;
+
+		SCAN: for (; c < endOffset; c = nextLF(buf, c)) {
+			switch (buf[c]) {
+			case ' ':
+			case '\n':
+				in = null;
+				oLine++;
+				nLine++;
+				continue;
+
+			case '-':
+				if (in == null) {
+					in = new Edit(oLine - 1, nLine - 1);
+					r.add(in);
+				}
+				oLine++;
+				in.extendA();
+				continue;
+
+			case '+':
+				if (in == null) {
+					in = new Edit(oLine - 1, nLine - 1);
+					r.add(in);
+				}
+				nLine++;
+				in.extendB();
+				continue;
+
+			case '\\': // Matches "\ No newline at end of file"
+				continue;
+
+			default:
+				break SCAN;
+			}
+		}
+		return r;
+	}
+
 	void parseHeader() {
 		// Parse "@@ -236,9 +236,9 @@ protected boolean"
 		//

diff --git a/org.spearce.jgit/src/org/spearce/jgit/diff/DiffFormatter.java b/org.spearce.jgit/src/org/spearce/jgit/diff/DiffFormatter.java
new file mode 100644
index 0000000..aa0f4a6
--- /dev/null
+++ b/org.spearce.jgit/src/org/spearce/jgit/diff/DiffFormatter.java
@@ -0,0 +1,187 @@
+/*
+ * Copyright (C) 2008, Johannes E. Schindelin <johannes.schindelin@gmx.de>
+ * Copyright (C) 2009, Google Inc.
+ *
+ * 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 Git Development Community 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.spearce.jgit.diff;
+
+import static org.spearce.jgit.lib.Constants.encodeASCII;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.util.List;
+
+import org.spearce.jgit.patch.FileHeader;
+
+/**
+ * Format an {@link EditList} as a Git style unified patch script.
+ */
+public class DiffFormatter {
+	private int context;
+
+	/** Create a new formatter with a default level of context. */
+	public DiffFormatter() {
+		setContext(3);
+	}
+
+	/**
+	 * Change the number of lines of context to display.
+	 * 
+	 * @param lineCount
+	 *            number of lines of context to see before the first
+	 *            modification and after the last modification within a hunk of
+	 *            the modified file.
+	 */
+	public void setContext(final int lineCount) {
+		if (lineCount < 0)
+			throw new IllegalArgumentException("context must be >= 0");
+		context = lineCount;
+	}
+
+	/**
+	 * Format a patch script, reusing a previously parsed FileHeader.
+	 * <p>
+	 * This formatter is primarily useful for editing an existing patch script
+	 * to increase or reduce the number of lines of context within the script.
+	 * All header lines are reused as-is from the supplied FileHeader.
+	 * 
+	 * @param out
+	 *            stream to write the patch script out to.
+	 * @param head
+	 *            existing file header containing the header lines to copy.
+	 * @param a
+	 *            text source for the pre-image version of the content. This
+	 *            must match the content of {@link FileHeader#getOldId()}.
+	 * @param b
+	 *            text source for the post-image version of the content. This
+	 *            must match the content of {@link FileHeader#getNewId()}.
+	 * @throws IOException
+	 *             writing to the supplied stream failed.
+	 */
+	public void format(final OutputStream out, final FileHeader head,
+			final RawText a, final RawText b)
+			throws IOException {
+		// Reuse the existing FileHeader as-is by blindly copying its
+		// header lines, but avoiding its hunks. Instead we recreate
+		// the hunks from the text instances we have been supplied.
+		//
+		final int start = head.getStartOffset();
+		int end = head.getEndOffset();
+		if (!head.getHunks().isEmpty())
+			end = head.getHunks().get(0).getStartOffset();
+		out.write(head.getBuffer(), start, end - start);
+
+		formatEdits(out, a, b, head.toEditList());
+	}
+
+	private void formatEdits(final OutputStream out, final RawText a,
+			final RawText b, final EditList edits) throws IOException {
+		for (int curIdx = 0; curIdx < edits.size();) {
+			Edit curEdit = edits.get(curIdx);
+			final int endIdx = findCombinedEnd(edits, curIdx);
+			final Edit endEdit = edits.get(endIdx);
+
+			int aCur = Math.max(0, curEdit.getBeginA() - context);
+			int bCur = Math.max(0, curEdit.getBeginB() - context);
+			final int aEnd = Math.min(a.size(), endEdit.getEndA() + context);
+			final int bEnd = Math.min(b.size(), endEdit.getEndB() + context);
+
+			out.write('@');
+			out.write('@');
+			writeLineGroup(out, '-', aCur + 1, aEnd - aCur);
+			writeLineGroup(out, '+', bCur + 1, bEnd - bCur);
+			out.write(' ');
+			out.write('@');
+			out.write('@');
+			out.write('\n');
+
+			while (aCur < aEnd || bCur < bEnd) {
+				if (aCur < curEdit.getBeginA() || endIdx + 1 < curIdx) {
+					out.write(' ');
+					a.writeLine(out, aCur);
+					out.write('\n');
+					aCur++;
+					bCur++;
+
+				} else if (aCur < curEdit.getEndA()) {
+					out.write('-');
+					a.writeLine(out, aCur);
+					out.write('\n');
+					aCur++;
+
+				} else if (bCur < curEdit.getEndB()) {
+					out.write('+');
+					b.writeLine(out, bCur);
+					out.write('\n');
+					bCur++;
+				}
+
+				if (!in(curEdit, aCur, bCur) && ++curIdx < edits.size())
+					curEdit = edits.get(curIdx);
+			}
+		}
+	}
+
+	private static void writeLineGroup(final OutputStream out,
+			final char prefix, final int begin, final int end)
+			throws IOException {
+		out.write(' ');
+		out.write(prefix);
+		out.write(encodeASCII(begin));
+		out.write(',');
+		out.write(encodeASCII(end));
+	}
+
+	private int findCombinedEnd(final List<Edit> edits, final int i) {
+		int end = i + 1;
+		while (end < edits.size()
+				&& (combineA(edits, end) || combineB(edits, end)))
+			end++;
+		return end - 1;
+	}
+
+	private boolean combineA(final List<Edit> e, final int i) {
+		return e.get(i).getBeginA() - e.get(i - 1).getEndA() <= 2 * context;
+	}
+
+	private boolean combineB(final List<Edit> e, final int i) {
+		return e.get(i).getBeginB() - e.get(i - 1).getEndB() <= 2 * context;
+	}
+
+	private static boolean in(final Edit edit, final int a, final int b) {
+		return a < edit.getEndA() && b < edit.getEndB();
+	}
+}

org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/E.patch, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/E_PostImage, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/E_PreImage, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/X.patch, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/X_PostImage, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/X_PreImage, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Y.patch, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Y_PostImage, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Y_PreImage, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Z.patch, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Z_PostImage, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Z_PreImage, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext1.out, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext10.out, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext100.out, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext3.out, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext5.out, org.spearce.jgit.test/tst/org/spearce/jgit/diff/DiffFormatterReflowTest.java, org.spearce.jgit/src/org/spearce/jgit/diff/DiffFormatter.java, org.spearce.jgit/src/org/spearce/jgit/diff/RawText.java

diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/E.patch b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/E.patch
new file mode 100644
index 0000000..9b8fa98
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/E.patch
@@ -0,0 +1,6 @@
+diff --git a/E b/E
+index e69de29..7898192 100644
+--- a/E
++++ b/E
+@@ -0,0 +1 @@
++a
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/E_PostImage b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/E_PostImage
new file mode 100644
index 0000000..7898192
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/E_PostImage
@@ -0,0 +1 @@
+a
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/E_PreImage b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/E_PreImage
new file mode 100644
index 0000000..e69de29
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/X.patch b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/X.patch
new file mode 100644
index 0000000..e5363eb
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/X.patch
@@ -0,0 +1,24 @@
+diff --git a/X b/X
+index a3648a1..2d44096 100644
+--- a/X
++++ b/X
+@@ -2,2 +2,3 @@ a
+ b
++c
+ d
+@@ -16,4 +17,2 @@ p
+ q
+-r
+-s
+ t
+@@ -22,4 +21,8 @@ v
+ w
+-x
+-y
++0
++1
++2
++3
++4
++5
+ z
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/X_PostImage b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/X_PostImage
new file mode 100644
index 0000000..2d44096
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/X_PostImage
@@ -0,0 +1,28 @@
+a
+b
+c
+d
+e
+f
+g
+h
+i
+j
+k
+l
+m
+n
+o
+p
+q
+t
+u
+v
+w
+0
+1
+2
+3
+4
+5
+z
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/X_PreImage b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/X_PreImage
new file mode 100644
index 0000000..a3648a1
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/X_PreImage
@@ -0,0 +1,25 @@
+a
+b
+d
+e
+f
+g
+h
+i
+j
+k
+l
+m
+n
+o
+p
+q
+r
+s
+t
+u
+v
+w
+x
+y
+z
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Y.patch b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Y.patch
new file mode 100644
index 0000000..a2c9a0b
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Y.patch
@@ -0,0 +1,8 @@
+diff --git a/Y b/Y
+index 2e65efe..7898192 100644
+--- a/Y
++++ b/Y
+@@ -1 +1 @@
+-a
+\ No newline at end of file
++a
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Y_PostImage b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Y_PostImage
new file mode 100644
index 0000000..7898192
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Y_PostImage
@@ -0,0 +1 @@
+a
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Y_PreImage b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Y_PreImage
new file mode 100644
index 0000000..2e65efe
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Y_PreImage
@@ -0,0 +1 @@
+a
\ No newline at end of file
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Z.patch b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Z.patch
new file mode 100644
index 0000000..35a06d6
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Z.patch
@@ -0,0 +1,8 @@
+diff --git a/Z b/Z
+index 7898192..2e65efe 100644
+--- a/Z
++++ b/Z
+@@ -1 +1 @@
+-a
++a
+\ No newline at end of file
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Z_PostImage b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Z_PostImage
new file mode 100644
index 0000000..2e65efe
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Z_PostImage
@@ -0,0 +1 @@
+a
\ No newline at end of file
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Z_PreImage b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Z_PreImage
new file mode 100644
index 0000000..7898192
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Z_PreImage
@@ -0,0 +1 @@
+a
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext1.out b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext1.out
new file mode 100644
index 0000000..d0d847d
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext1.out
@@ -0,0 +1,24 @@
+diff --git a/X b/X
+index a3648a1..2d44096 100644
+--- a/X
++++ b/X
+@@ -2,2 +2,3 @@
+ b
++c
+ d
+@@ -16,4 +17,2 @@
+ q
+-r
+-s
+ t
+@@ -22,4 +21,8 @@
+ w
+-x
+-y
++0
++1
++2
++3
++4
++5
+ z
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext10.out b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext10.out
new file mode 100644
index 0000000..1d4f242
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext10.out
@@ -0,0 +1,37 @@
+diff --git a/X b/X
+index a3648a1..2d44096 100644
+--- a/X
++++ b/X
+@@ -1,25 +1,28 @@
+ a
+ b
++c
+ d
+ e
+ f
+ g
+ h
+ i
+ j
+ k
+ l
+ m
+ n
+ o
+ p
+ q
+-r
+-s
+ t
+ u
+ v
+ w
+-x
+-y
++0
++1
++2
++3
++4
++5
+ z
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext100.out b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext100.out
new file mode 100644
index 0000000..1d4f242
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext100.out
@@ -0,0 +1,37 @@
+diff --git a/X b/X
+index a3648a1..2d44096 100644
+--- a/X
++++ b/X
+@@ -1,25 +1,28 @@
+ a
+ b
++c
+ d
+ e
+ f
+ g
+ h
+ i
+ j
+ k
+ l
+ m
+ n
+ o
+ p
+ q
+-r
+-s
+ t
+ u
+ v
+ w
+-x
+-y
++0
++1
++2
++3
++4
++5
+ z
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext3.out b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext3.out
new file mode 100644
index 0000000..2564016
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext3.out
@@ -0,0 +1,30 @@
+diff --git a/X b/X
+index a3648a1..2d44096 100644
+--- a/X
++++ b/X
+@@ -1,5 +1,6 @@
+ a
+ b
++c
+ d
+ e
+ f
+@@ -14,12 +15,14 @@
+ o
+ p
+ q
+-r
+-s
+ t
+ u
+ v
+ w
+-x
+-y
++0
++1
++2
++3
++4
++5
+ z
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext5.out b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext5.out
new file mode 100644
index 0000000..3073c5f
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext5.out
@@ -0,0 +1,34 @@
+diff --git a/X b/X
+index a3648a1..2d44096 100644
+--- a/X
++++ b/X
+@@ -1,7 +1,8 @@
+ a
+ b
++c
+ d
+ e
+ f
+ g
+ h
+@@ -12,14 +13,16 @@
+ m
+ n
+ o
+ p
+ q
+-r
+-s
+ t
+ u
+ v
+ w
+-x
+-y
++0
++1
++2
++3
++4
++5
+ z
diff --git a/org.spearce.jgit.test/tst/org/spearce/jgit/diff/DiffFormatterReflowTest.java b/org.spearce.jgit.test/tst/org/spearce/jgit/diff/DiffFormatterReflowTest.java
new file mode 100644
index 0000000..f47282c
--- /dev/null
+++ b/org.spearce.jgit.test/tst/org/spearce/jgit/diff/DiffFormatterReflowTest.java
@@ -0,0 +1,170 @@
+/*
+ * Copyright (C) 2009, Google Inc.
+ *
+ * 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 Git Development Community 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.spearce.jgit.diff;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+
+import junit.framework.TestCase;
+
+import org.spearce.jgit.patch.FileHeader;
+import org.spearce.jgit.patch.Patch;
+import org.spearce.jgit.util.RawParseUtils;
+
+public class DiffFormatterReflowTest extends TestCase {
+	private RawText a;
+
+	private RawText b;
+
+	private FileHeader file;
+
+	private ByteArrayOutputStream out;
+
+	private DiffFormatter fmt;
+
+	protected void setUp() throws Exception {
+		super.setUp();
+		out = new ByteArrayOutputStream();
+		fmt = new DiffFormatter();
+	}
+
+	public void testNegativeContextFails() throws IOException {
+		init("X");
+		try {
+			fmt.setContext(-1);
+			fail("accepted negative context");
+		} catch (IllegalArgumentException e) {
+			// pass
+		}
+	}
+
+	public void testContext1() throws IOException {
+		init("X");
+		fmt.setContext(1);
+		assertFormatted();
+	}
+
+	public void testContext3() throws IOException {
+		init("X");
+		fmt.setContext(3);
+		assertFormatted();
+	}
+
+	public void testContext5() throws IOException {
+		init("X");
+		fmt.setContext(5);
+		assertFormatted();
+	}
+
+	public void testContext10() throws IOException {
+		init("X");
+		fmt.setContext(10);
+		assertFormatted();
+	}
+
+	public void testContext100() throws IOException {
+		init("X");
+		fmt.setContext(100);
+		assertFormatted();
+	}
+
+	public void testEmpty1() throws IOException {
+		init("E");
+		assertFormatted("E.patch");
+	}
+
+	public void testNoNewLine1() throws IOException {
+		init("Y");
+		assertFormatted("Y.patch");
+	}
+
+	public void testNoNewLine2() throws IOException {
+		init("Z");
+		assertFormatted("Z.patch");
+	}
+
+	private void init(final String name) throws IOException {
+		a = new RawText(readFile(name + "_PreImage"));
+		b = new RawText(readFile(name + "_PostImage"));
+		file = parseTestPatchFile(name + ".patch").getFiles().get(0);
+	}
+
+	private void assertFormatted() throws IOException {
+		assertFormatted(getName() + ".out");
+	}
+
+	private void assertFormatted(final String name) throws IOException {
+		fmt.format(out, file, a, b);
+		final String exp = RawParseUtils.decode(readFile(name));
+		assertEquals(exp, RawParseUtils.decode(out.toByteArray()));
+	}
+
+	private byte[] readFile(final String patchFile) throws IOException {
+		final InputStream in = getClass().getResourceAsStream(patchFile);
+		if (in == null) {
+			fail("No " + patchFile + " test vector");
+			return null; // Never happens
+		}
+		try {
+			final byte[] buf = new byte[1024];
+			final ByteArrayOutputStream temp = new ByteArrayOutputStream();
+			int n;
+			while ((n = in.read(buf)) > 0)
+				temp.write(buf, 0, n);
+			return temp.toByteArray();
+		} finally {
+			in.close();
+		}
+	}
+
+	private Patch parseTestPatchFile(final String patchFile) throws IOException {
+		final InputStream in = getClass().getResourceAsStream(patchFile);
+		if (in == null) {
+			fail("No " + patchFile + " test vector");
+			return null; // Never happens
+		}
+		try {
+			final Patch p = new Patch();
+			p.parse(in);
+			return p;
+		} finally {
+			in.close();
+		}
+	}
+}
diff --git a/org.spearce.jgit/src/org/spearce/jgit/diff/DiffFormatter.java b/org.spearce.jgit/src/org/spearce/jgit/diff/DiffFormatter.java
new file mode 100644
index 0000000..97db9a2
--- /dev/null
+++ b/org.spearce.jgit/src/org/spearce/jgit/diff/DiffFormatter.java
@@ -0,0 +1,220 @@
+/*
+ * Copyright (C) 2008, Johannes E. Schindelin <johannes.schindelin@gmx.de>
+ * Copyright (C) 2009, Google Inc.
+ *
+ * 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 Git Development Community 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.spearce.jgit.diff;
+
+import static org.spearce.jgit.lib.Constants.encodeASCII;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.util.List;
+
+import org.spearce.jgit.patch.FileHeader;
+
+/**
+ * Format an {@link EditList} as a Git style unified patch script.
+ */
+public class DiffFormatter {
+	private static final byte[] noNewLine = encodeASCII("\\ No newline at end of file\n");
+
+	private int context;
+
+	/** Create a new formatter with a default level of context. */
+	public DiffFormatter() {
+		setContext(3);
+	}
+
+	/**
+	 * Change the number of lines of context to display.
+	 * 
+	 * @param lineCount
+	 *            number of lines of context to see before the first
+	 *            modification and after the last modification within a hunk of
+	 *            the modified file.
+	 */
+	public void setContext(final int lineCount) {
+		if (lineCount < 0)
+			throw new IllegalArgumentException("context must be >= 0");
+		context = lineCount;
+	}
+
+	/**
+	 * Format a patch script, reusing a previously parsed FileHeader.
+	 * <p>
+	 * This formatter is primarily useful for editing an existing patch script
+	 * to increase or reduce the number of lines of context within the script.
+	 * All header lines are reused as-is from the supplied FileHeader.
+	 * 
+	 * @param out
+	 *            stream to write the patch script out to.
+	 * @param head
+	 *            existing file header containing the header lines to copy.
+	 * @param a
+	 *            text source for the pre-image version of the content. This
+	 *            must match the content of {@link FileHeader#getOldId()}.
+	 * @param b
+	 *            text source for the post-image version of the content. This
+	 *            must match the content of {@link FileHeader#getNewId()}.
+	 * @throws IOException
+	 *             writing to the supplied stream failed.
+	 */
+	public void format(final OutputStream out, final FileHeader head,
+			final RawText a, final RawText b) throws IOException {
+		// Reuse the existing FileHeader as-is by blindly copying its
+		// header lines, but avoiding its hunks. Instead we recreate
+		// the hunks from the text instances we have been supplied.
+		//
+		final int start = head.getStartOffset();
+		int end = head.getEndOffset();
+		if (!head.getHunks().isEmpty())
+			end = head.getHunks().get(0).getStartOffset();
+		out.write(head.getBuffer(), start, end - start);
+
+		formatEdits(out, a, b, head.toEditList());
+	}
+
+	private void formatEdits(final OutputStream out, final RawText a,
+			final RawText b, final EditList edits) throws IOException {
+		for (int curIdx = 0; curIdx < edits.size();) {
+			Edit curEdit = edits.get(curIdx);
+			final int endIdx = findCombinedEnd(edits, curIdx);
+			final Edit endEdit = edits.get(endIdx);
+
+			int aCur = Math.max(0, curEdit.getBeginA() - context);
+			int bCur = Math.max(0, curEdit.getBeginB() - context);
+			final int aEnd = Math.min(a.size(), endEdit.getEndA() + context);
+			final int bEnd = Math.min(b.size(), endEdit.getEndB() + context);
+
+			writeHunkHeader(out, aCur, aEnd, bCur, bEnd, curIdx == 0);
+
+			while (aCur < aEnd || bCur < bEnd) {
+				if (aCur < curEdit.getBeginA() || endIdx + 1 < curIdx) {
+					writeLine(out, ' ', a, aCur);
+					aCur++;
+					bCur++;
+
+				} else if (aCur < curEdit.getEndA()) {
+					writeLine(out, '-', a, aCur++);
+
+				} else if (bCur < curEdit.getEndB()) {
+					writeLine(out, '+', b, bCur++);
+				}
+
+				if (end(curEdit, aCur, bCur) && ++curIdx < edits.size())
+					curEdit = edits.get(curIdx);
+			}
+		}
+	}
+
+	private void writeHunkHeader(final OutputStream out, final int aCur,
+			final int aEnd, final int bCur, final int bEnd,
+			final boolean firstHunk) throws IOException {
+		out.write('@');
+		out.write('@');
+		if (firstHunk) {
+			writeFirstLineGroup(out, '-', aCur + 1, aEnd - aCur);
+			writeFirstLineGroup(out, '+', bCur + 1, bEnd - bCur);
+		} else {
+			writeAnyLineGroup(out, '-', aCur + 1, aEnd - aCur);
+			writeAnyLineGroup(out, '+', bCur + 1, bEnd - bCur);
+		}
+		out.write(' ');
+		out.write('@');
+		out.write('@');
+		out.write('\n');
+	}
+
+	private static void writeFirstLineGroup(final OutputStream out,
+			final char prefix, final int begin, final int cnt)
+			throws IOException {
+		if (begin == 1 && cnt == 0) {
+			out.write(' ');
+			out.write(prefix);
+			out.write('0');
+			out.write(',');
+			out.write('0');
+
+		} else if (cnt == 1) {
+			out.write(' ');
+			out.write(prefix);
+			out.write(encodeASCII(begin));
+
+		} else {
+			writeAnyLineGroup(out, prefix, begin, cnt);
+		}
+	}
+
+	private static void writeAnyLineGroup(final OutputStream out,
+			final char prefix, final int begin, final int cnt)
+			throws IOException {
+		out.write(' ');
+		out.write(prefix);
+		out.write(encodeASCII(begin));
+		out.write(',');
+		out.write(encodeASCII(cnt));
+	}
+
+	private static void writeLine(final OutputStream out, final char prefix,
+			final RawText text, final int cur) throws IOException {
+		out.write(prefix);
+		text.writeLine(out, cur);
+		out.write('\n');
+		if (cur + 1 == text.size() && text.isMissingNewlineAtEnd())
+			out.write(noNewLine);
+	}
+
+	private int findCombinedEnd(final List<Edit> edits, final int i) {
+		int end = i + 1;
+		while (end < edits.size()
+				&& (combineA(edits, end) || combineB(edits, end)))
+			end++;
+		return end - 1;
+	}
+
+	private boolean combineA(final List<Edit> e, final int i) {
+		return e.get(i).getBeginA() - e.get(i - 1).getEndA() <= 2 * context;
+	}
+
+	private boolean combineB(final List<Edit> e, final int i) {
+		return e.get(i).getBeginB() - e.get(i - 1).getEndB() <= 2 * context;
+	}
+
+	private static boolean end(final Edit edit, final int a, final int b) {
+		return edit.getEndA() <= a && edit.getEndB() <= b;
+	}
+}
diff --git a/org.spearce.jgit/src/org/spearce/jgit/diff/RawText.java b/org.spearce.jgit/src/org/spearce/jgit/diff/RawText.java
index 1d10082..e10ee46 100644
--- a/org.spearce.jgit/src/org/spearce/jgit/diff/RawText.java
+++ b/org.spearce.jgit/src/org/spearce/jgit/diff/RawText.java
@@ -140,6 +140,18 @@ public void writeLine(final OutputStream out, final int i)
 		out.write(content, start, end - start);
 	}
 
+	/**
+	 * Determine if the file ends with a LF ('\n').
+	 * 
+	 * @return true if the last line has an LF; false otherwise.
+	 */
+	public boolean isMissingNewlineAtEnd() {
+		final int end = lines.get(lines.size() - 1);
+		if (end == 0)
+			return true;
+		return content[end - 1] != '\n';
+	}
+
 	private IntList computeHashes() {
 		final IntList r = new IntList(lines.size());
 		r.add(0);

org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/E.patch, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/E_PostImage, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/E_PreImage, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/X.patch, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/X_PostImage, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/X_PreImage, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Y.patch, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Y_PostImage, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Y_PreImage, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Z.patch, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Z_PostImage, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Z_PreImage, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext0.out, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext1.out, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext10.out, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext100.out, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext3.out, org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext5.out, org.spearce.jgit.test/tst/org/spearce/jgit/diff/DiffFormatterReflowTest.java, org.spearce.jgit/src/org/spearce/jgit/diff/DiffFormatter.java, org.spearce.jgit/src/org/spearce/jgit/diff/RawText.java

diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/E.patch b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/E.patch
new file mode 100644
index 0000000..9b8fa98
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/E.patch
@@ -0,0 +1,6 @@
+diff --git a/E b/E
+index e69de29..7898192 100644
+--- a/E
++++ b/E
+@@ -0,0 +1 @@
++a
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/E_PostImage b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/E_PostImage
new file mode 100644
index 0000000..7898192
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/E_PostImage
@@ -0,0 +1 @@
+a
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/E_PreImage b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/E_PreImage
new file mode 100644
index 0000000..e69de29
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/X.patch b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/X.patch
new file mode 100644
index 0000000..e5363eb
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/X.patch
@@ -0,0 +1,24 @@
+diff --git a/X b/X
+index a3648a1..2d44096 100644
+--- a/X
++++ b/X
+@@ -2,2 +2,3 @@ a
+ b
++c
+ d
+@@ -16,4 +17,2 @@ p
+ q
+-r
+-s
+ t
+@@ -22,4 +21,8 @@ v
+ w
+-x
+-y
++0
++1
++2
++3
++4
++5
+ z
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/X_PostImage b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/X_PostImage
new file mode 100644
index 0000000..2d44096
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/X_PostImage
@@ -0,0 +1,28 @@
+a
+b
+c
+d
+e
+f
+g
+h
+i
+j
+k
+l
+m
+n
+o
+p
+q
+t
+u
+v
+w
+0
+1
+2
+3
+4
+5
+z
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/X_PreImage b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/X_PreImage
new file mode 100644
index 0000000..a3648a1
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/X_PreImage
@@ -0,0 +1,25 @@
+a
+b
+d
+e
+f
+g
+h
+i
+j
+k
+l
+m
+n
+o
+p
+q
+r
+s
+t
+u
+v
+w
+x
+y
+z
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Y.patch b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Y.patch
new file mode 100644
index 0000000..a2c9a0b
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Y.patch
@@ -0,0 +1,8 @@
+diff --git a/Y b/Y
+index 2e65efe..7898192 100644
+--- a/Y
++++ b/Y
+@@ -1 +1 @@
+-a
+\ No newline at end of file
++a
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Y_PostImage b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Y_PostImage
new file mode 100644
index 0000000..7898192
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Y_PostImage
@@ -0,0 +1 @@
+a
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Y_PreImage b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Y_PreImage
new file mode 100644
index 0000000..2e65efe
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Y_PreImage
@@ -0,0 +1 @@
+a
\ No newline at end of file
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Z.patch b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Z.patch
new file mode 100644
index 0000000..35a06d6
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Z.patch
@@ -0,0 +1,8 @@
+diff --git a/Z b/Z
+index 7898192..2e65efe 100644
+--- a/Z
++++ b/Z
+@@ -1 +1 @@
+-a
++a
+\ No newline at end of file
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Z_PostImage b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Z_PostImage
new file mode 100644
index 0000000..2e65efe
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Z_PostImage
@@ -0,0 +1 @@
+a
\ No newline at end of file
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Z_PreImage b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Z_PreImage
new file mode 100644
index 0000000..7898192
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/Z_PreImage
@@ -0,0 +1 @@
+a
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext0.out b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext0.out
new file mode 100644
index 0000000..d36e3fa
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext0.out
@@ -0,0 +1,18 @@
+diff --git a/X b/X
+index a3648a1..2d44096 100644
+--- a/X
++++ b/X
+@@ -2,0 +3 @@
++c
+@@ -17,2 +17,0 @@
+-r
+-s
+@@ -23,2 +22,6 @@
+-x
+-y
++0
++1
++2
++3
++4
++5
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext1.out b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext1.out
new file mode 100644
index 0000000..d0d847d
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext1.out
@@ -0,0 +1,24 @@
+diff --git a/X b/X
+index a3648a1..2d44096 100644
+--- a/X
++++ b/X
+@@ -2,2 +2,3 @@
+ b
++c
+ d
+@@ -16,4 +17,2 @@
+ q
+-r
+-s
+ t
+@@ -22,4 +21,8 @@
+ w
+-x
+-y
++0
++1
++2
++3
++4
++5
+ z
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext10.out b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext10.out
new file mode 100644
index 0000000..1d4f242
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext10.out
@@ -0,0 +1,37 @@
+diff --git a/X b/X
+index a3648a1..2d44096 100644
+--- a/X
++++ b/X
+@@ -1,25 +1,28 @@
+ a
+ b
++c
+ d
+ e
+ f
+ g
+ h
+ i
+ j
+ k
+ l
+ m
+ n
+ o
+ p
+ q
+-r
+-s
+ t
+ u
+ v
+ w
+-x
+-y
++0
++1
++2
++3
++4
++5
+ z
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext100.out b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext100.out
new file mode 100644
index 0000000..1d4f242
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext100.out
@@ -0,0 +1,37 @@
+diff --git a/X b/X
+index a3648a1..2d44096 100644
+--- a/X
++++ b/X
+@@ -1,25 +1,28 @@
+ a
+ b
++c
+ d
+ e
+ f
+ g
+ h
+ i
+ j
+ k
+ l
+ m
+ n
+ o
+ p
+ q
+-r
+-s
+ t
+ u
+ v
+ w
+-x
+-y
++0
++1
++2
++3
++4
++5
+ z
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext3.out b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext3.out
new file mode 100644
index 0000000..2564016
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext3.out
@@ -0,0 +1,30 @@
+diff --git a/X b/X
+index a3648a1..2d44096 100644
+--- a/X
++++ b/X
+@@ -1,5 +1,6 @@
+ a
+ b
++c
+ d
+ e
+ f
+@@ -14,12 +15,14 @@
+ o
+ p
+ q
+-r
+-s
+ t
+ u
+ v
+ w
+-x
+-y
++0
++1
++2
++3
++4
++5
+ z
diff --git a/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext5.out b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext5.out
new file mode 100644
index 0000000..3073c5f
--- /dev/null
+++ b/org.spearce.jgit.test/tst-rsrc/org/spearce/jgit/diff/testContext5.out
@@ -0,0 +1,34 @@
+diff --git a/X b/X
+index a3648a1..2d44096 100644
+--- a/X
++++ b/X
+@@ -1,7 +1,8 @@
+ a
+ b
++c
+ d
+ e
+ f
+ g
+ h
+@@ -12,14 +13,16 @@
+ m
+ n
+ o
+ p
+ q
+-r
+-s
+ t
+ u
+ v
+ w
+-x
+-y
++0
++1
++2
++3
++4
++5
+ z
diff --git a/org.spearce.jgit.test/tst/org/spearce/jgit/diff/DiffFormatterReflowTest.java b/org.spearce.jgit.test/tst/org/spearce/jgit/diff/DiffFormatterReflowTest.java
new file mode 100644
index 0000000..5d2ee40
--- /dev/null
+++ b/org.spearce.jgit.test/tst/org/spearce/jgit/diff/DiffFormatterReflowTest.java
@@ -0,0 +1,176 @@
+/*
+ * Copyright (C) 2009, Google Inc.
+ *
+ * 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 Git Development Community 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.spearce.jgit.diff;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+
+import junit.framework.TestCase;
+
+import org.spearce.jgit.patch.FileHeader;
+import org.spearce.jgit.patch.Patch;
+import org.spearce.jgit.util.RawParseUtils;
+
+public class DiffFormatterReflowTest extends TestCase {
+	private RawText a;
+
+	private RawText b;
+
+	private FileHeader file;
+
+	private ByteArrayOutputStream out;
+
+	private DiffFormatter fmt;
+
+	protected void setUp() throws Exception {
+		super.setUp();
+		out = new ByteArrayOutputStream();
+		fmt = new DiffFormatter();
+	}
+
+	public void testNegativeContextFails() throws IOException {
+		init("X");
+		try {
+			fmt.setContext(-1);
+			fail("accepted negative context");
+		} catch (IllegalArgumentException e) {
+			// pass
+		}
+	}
+
+	public void testContext0() throws IOException {
+		init("X");
+		fmt.setContext(0);
+		assertFormatted();
+	}
+
+	public void testContext1() throws IOException {
+		init("X");
+		fmt.setContext(1);
+		assertFormatted();
+	}
+
+	public void testContext3() throws IOException {
+		init("X");
+		fmt.setContext(3);
+		assertFormatted();
+	}
+
+	public void testContext5() throws IOException {
+		init("X");
+		fmt.setContext(5);
+		assertFormatted();
+	}
+
+	public void testContext10() throws IOException {
+		init("X");
+		fmt.setContext(10);
+		assertFormatted();
+	}
+
+	public void testContext100() throws IOException {
+		init("X");
+		fmt.setContext(100);
+		assertFormatted();
+	}
+
+	public void testEmpty1() throws IOException {
+		init("E");
+		assertFormatted("E.patch");
+	}
+
+	public void testNoNewLine1() throws IOException {
+		init("Y");
+		assertFormatted("Y.patch");
+	}
+
+	public void testNoNewLine2() throws IOException {
+		init("Z");
+		assertFormatted("Z.patch");
+	}
+
+	private void init(final String name) throws IOException {
+		a = new RawText(readFile(name + "_PreImage"));
+		b = new RawText(readFile(name + "_PostImage"));
+		file = parseTestPatchFile(name + ".patch").getFiles().get(0);
+	}
+
+	private void assertFormatted() throws IOException {
+		assertFormatted(getName() + ".out");
+	}
+
+	private void assertFormatted(final String name) throws IOException {
+		fmt.format(out, file, a, b);
+		final String exp = RawParseUtils.decode(readFile(name));
+		assertEquals(exp, RawParseUtils.decode(out.toByteArray()));
+	}
+
+	private byte[] readFile(final String patchFile) throws IOException {
+		final InputStream in = getClass().getResourceAsStream(patchFile);
+		if (in == null) {
+			fail("No " + patchFile + " test vector");
+			return null; // Never happens
+		}
+		try {
+			final byte[] buf = new byte[1024];
+			final ByteArrayOutputStream temp = new ByteArrayOutputStream();
+			int n;
+			while ((n = in.read(buf)) > 0)
+				temp.write(buf, 0, n);
+			return temp.toByteArray();
+		} finally {
+			in.close();
+		}
+	}
+
+	private Patch parseTestPatchFile(final String patchFile) throws IOException {
+		final InputStream in = getClass().getResourceAsStream(patchFile);
+		if (in == null) {
+			fail("No " + patchFile + " test vector");
+			return null; // Never happens
+		}
+		try {
+			final Patch p = new Patch();
+			p.parse(in);
+			return p;
+		} finally {
+			in.close();
+		}
+	}
+}
diff --git a/org.spearce.jgit/src/org/spearce/jgit/diff/DiffFormatter.java b/org.spearce.jgit/src/org/spearce/jgit/diff/DiffFormatter.java
new file mode 100644
index 0000000..9a81901
--- /dev/null
+++ b/org.spearce.jgit/src/org/spearce/jgit/diff/DiffFormatter.java
@@ -0,0 +1,214 @@
+/*
+ * Copyright (C) 2008, Johannes E. Schindelin <johannes.schindelin@gmx.de>
+ * Copyright (C) 2009, Google Inc.
+ *
+ * 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 Git Development Community 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.spearce.jgit.diff;
+
+import static org.spearce.jgit.lib.Constants.encodeASCII;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.util.List;
+
+import org.spearce.jgit.patch.FileHeader;
+
+/**
+ * Format an {@link EditList} as a Git style unified patch script.
+ */
+public class DiffFormatter {
+	private static final byte[] noNewLine = encodeASCII("\\ No newline at end of file\n");
+
+	private int context;
+
+	/** Create a new formatter with a default level of context. */
+	public DiffFormatter() {
+		setContext(3);
+	}
+
+	/**
+	 * Change the number of lines of context to display.
+	 * 
+	 * @param lineCount
+	 *            number of lines of context to see before the first
+	 *            modification and after the last modification within a hunk of
+	 *            the modified file.
+	 */
+	public void setContext(final int lineCount) {
+		if (lineCount < 0)
+			throw new IllegalArgumentException("context must be >= 0");
+		context = lineCount;
+	}
+
+	/**
+	 * Format a patch script, reusing a previously parsed FileHeader.
+	 * <p>
+	 * This formatter is primarily useful for editing an existing patch script
+	 * to increase or reduce the number of lines of context within the script.
+	 * All header lines are reused as-is from the supplied FileHeader.
+	 * 
+	 * @param out
+	 *            stream to write the patch script out to.
+	 * @param head
+	 *            existing file header containing the header lines to copy.
+	 * @param a
+	 *            text source for the pre-image version of the content. This
+	 *            must match the content of {@link FileHeader#getOldId()}.
+	 * @param b
+	 *            text source for the post-image version of the content. This
+	 *            must match the content of {@link FileHeader#getNewId()}.
+	 * @throws IOException
+	 *             writing to the supplied stream failed.
+	 */
+	public void format(final OutputStream out, final FileHeader head,
+			final RawText a, final RawText b) throws IOException {
+		// Reuse the existing FileHeader as-is by blindly copying its
+		// header lines, but avoiding its hunks. Instead we recreate
+		// the hunks from the text instances we have been supplied.
+		//
+		final int start = head.getStartOffset();
+		int end = head.getEndOffset();
+		if (!head.getHunks().isEmpty())
+			end = head.getHunks().get(0).getStartOffset();
+		out.write(head.getBuffer(), start, end - start);
+
+		formatEdits(out, a, b, head.toEditList());
+	}
+
+	private void formatEdits(final OutputStream out, final RawText a,
+			final RawText b, final EditList edits) throws IOException {
+		for (int curIdx = 0; curIdx < edits.size();) {
+			Edit curEdit = edits.get(curIdx);
+			final int endIdx = findCombinedEnd(edits, curIdx);
+			final Edit endEdit = edits.get(endIdx);
+
+			int aCur = Math.max(0, curEdit.getBeginA() - context);
+			int bCur = Math.max(0, curEdit.getBeginB() - context);
+			final int aEnd = Math.min(a.size(), endEdit.getEndA() + context);
+			final int bEnd = Math.min(b.size(), endEdit.getEndB() + context);
+
+			writeHunkHeader(out, aCur, aEnd, bCur, bEnd);
+
+			while (aCur < aEnd || bCur < bEnd) {
+				if (aCur < curEdit.getBeginA() || endIdx + 1 < curIdx) {
+					writeLine(out, ' ', a, aCur);
+					aCur++;
+					bCur++;
+
+				} else if (aCur < curEdit.getEndA()) {
+					writeLine(out, '-', a, aCur++);
+
+				} else if (bCur < curEdit.getEndB()) {
+					writeLine(out, '+', b, bCur++);
+				}
+
+				if (end(curEdit, aCur, bCur) && ++curIdx < edits.size())
+					curEdit = edits.get(curIdx);
+			}
+		}
+	}
+
+	private void writeHunkHeader(final OutputStream out, int aCur, int aEnd,
+			int bCur, int bEnd) throws IOException {
+		out.write('@');
+		out.write('@');
+		writeRange(out, '-', aCur + 1, aEnd - aCur);
+		writeRange(out, '+', bCur + 1, bEnd - bCur);
+		out.write(' ');
+		out.write('@');
+		out.write('@');
+		out.write('\n');
+	}
+
+	private static void writeRange(final OutputStream out, final char prefix,
+			final int begin, final int cnt) throws IOException {
+		out.write(' ');
+		out.write(prefix);
+		switch (cnt) {
+		case 0:
+			// If the range is empty, its beginning number must be the
+			// line just before the range, or 0 if the range is at the
+			// start of the file stream. Here, begin is always 1 based,
+			// so an empty file would produce "0,0".
+			//
+			out.write(encodeASCII(begin - 1));
+			out.write(',');
+			out.write('0');
+			break;
+
+		case 1:
+			// If the range is exactly one line, produce only the number.
+			//
+			out.write(encodeASCII(begin));
+			break;
+
+		default:
+			out.write(encodeASCII(begin));
+			out.write(',');
+			out.write(encodeASCII(cnt));
+			break;
+		}
+	}
+
+	private static void writeLine(final OutputStream out, final char prefix,
+			final RawText text, final int cur) throws IOException {
+		out.write(prefix);
+		text.writeLine(out, cur);
+		out.write('\n');
+		if (cur + 1 == text.size() && text.isMissingNewlineAtEnd())
+			out.write(noNewLine);
+	}
+
+	private int findCombinedEnd(final List<Edit> edits, final int i) {
+		int end = i + 1;
+		while (end < edits.size()
+				&& (combineA(edits, end) || combineB(edits, end)))
+			end++;
+		return end - 1;
+	}
+
+	private boolean combineA(final List<Edit> e, final int i) {
+		return e.get(i).getBeginA() - e.get(i - 1).getEndA() <= 2 * context;
+	}
+
+	private boolean combineB(final List<Edit> e, final int i) {
+		return e.get(i).getBeginB() - e.get(i - 1).getEndB() <= 2 * context;
+	}
+
+	private static boolean end(final Edit edit, final int a, final int b) {
+		return edit.getEndA() <= a && edit.getEndB() <= b;
+	}
+}
diff --git a/org.spearce.jgit/src/org/spearce/jgit/diff/RawText.java b/org.spearce.jgit/src/org/spearce/jgit/diff/RawText.java
index 1d10082..e10ee46 100644
--- a/org.spearce.jgit/src/org/spearce/jgit/diff/RawText.java
+++ b/org.spearce.jgit/src/org/spearce/jgit/diff/RawText.java
@@ -140,6 +140,18 @@ public void writeLine(final OutputStream out, final int i)
 		out.write(content, start, end - start);
 	}
 
+	/**
+	 * Determine if the file ends with a LF ('\n').
+	 * 
+	 * @return true if the last line has an LF; false otherwise.
+	 */
+	public boolean isMissingNewlineAtEnd() {
+		final int end = lines.get(lines.size() - 1);
+		if (end == 0)
+			return true;
+		return content[end - 1] != '\n';
+	}
+
 	private IntList computeHashes() {
 		final IntList r = new IntList(lines.size());
 		r.add(0);