Merge "Add helper methods to Edit"

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

@@ -61,6 +61,8 @@ public class EditTest extends TestCase {
 		assertEquals(1, e.getEndA());
 		assertEquals(3, e.getBeginB());
 		assertEquals(3, e.getEndB());
+		assertTrue("is empty", e.isEmpty());
+		assertSame(Edit.Type.EMPTY, e.getType());
 	}
 
 	public void testSwap() {
@@ -75,21 +77,34 @@ public class EditTest extends TestCase {
 	public void testType_Insert() {
 		final Edit e = new Edit(1, 1, 1, 2);
 		assertSame(Edit.Type.INSERT, e.getType());
+		assertFalse("not empty", e.isEmpty());
+		assertEquals(0, e.getLengthA());
+		assertEquals(1, e.getLengthB());
 	}
 
 	public void testType_Delete() {
 		final Edit e = new Edit(1, 2, 1, 1);
 		assertSame(Edit.Type.DELETE, e.getType());
+		assertFalse("not empty", e.isEmpty());
+		assertEquals(1, e.getLengthA());
+		assertEquals(0, e.getLengthB());
 	}
 
 	public void testType_Replace() {
 		final Edit e = new Edit(1, 2, 1, 4);
 		assertSame(Edit.Type.REPLACE, e.getType());
+		assertFalse("not empty", e.isEmpty());
+		assertEquals(1, e.getLengthA());
+		assertEquals(3, e.getLengthB());
 	}
 
 	public void testType_Empty() {
-		assertSame(Edit.Type.EMPTY, new Edit(1, 1, 2, 2).getType());
+		final Edit e = new Edit(1, 1, 2, 2);
+		assertSame(Edit.Type.EMPTY, e.getType());
 		assertSame(Edit.Type.EMPTY, new Edit(1, 2).getType());
+		assertTrue("is empty", e.isEmpty());
+		assertEquals(0, e.getLengthA());
+		assertEquals(0, e.getLengthB());
 	}
 
 	public void testToString() {
@@ -143,4 +158,12 @@ public class EditTest extends TestCase {
 		e.extendB();
 		assertEquals(new Edit(1, 2, 1, 3), e);
 	}
+
+	public void testBeforeAfterCuts() {
+		final Edit whole = new Edit(1, 8, 2, 9);
+		final Edit mid = new Edit(4, 5, 3, 6);
+
+		assertEquals(new Edit(1, 4, 2, 3), whole.before(mid));
+		assertEquals(new Edit(5, 8, 6, 9), whole.after(mid));
+	}
 }

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

@@ -130,6 +130,11 @@ public class Edit {
 		return Type.REPLACE;
 	}
 
+	/** @return true if the edit is empty (lengths of both a and b is zero). */
+	public final boolean isEmpty() {
+		return beginA == endA && beginB == endB;
+	}
+
 	/** @return start point in sequence A. */
 	public final int getBeginA() {
 		return beginA;
@@ -150,6 +155,42 @@ public class Edit {
 		return endB;
 	}
 
+	/** @return length of the region in A. */
+	public final int getLengthA() {
+		return endA - beginA;
+	}
+
+	/** @return length of the region in B. */
+	public final int getLengthB() {
+		return endB - beginB;
+	}
+
+	/**
+	 * Construct a new edit representing the region before cut.
+	 *
+	 * @param cut
+	 *            the cut point. The beginning A and B points are used as the
+	 *            end points of the returned edit.
+	 * @return an edit representing the slice of {@code this} edit that occurs
+	 *         before {@code cut} starts.
+	 */
+	public final Edit before(Edit cut) {
+		return new Edit(beginA, cut.beginA, beginB, cut.beginB);
+	}
+
+	/**
+	 * Construct a new edit representing the region after cut.
+	 *
+	 * @param cut
+	 *            the cut point. The ending A and B points are used as the
+	 *            starting points of the returned edit.
+	 * @return an edit representing the slice of {@code this} edit that occurs
+	 *         after {@code cut} ends.
+	 */
+	public final Edit after(Edit cut) {
+		return new Edit(cut.endA, endA, cut.endB, endB);
+	}
+
 	/** Increase {@link #getEndA()} by 1. */
 	public void extendA() {
 		endA++;