Skip a number commits before starting to show the commit output

Change-Id: Id2666d897d29b6371f7a6cf241cfda02964b4971
Signed-off-by: Kevin Sawicki <kevin@github.com>

4 files changed, 120 insertions, 2 deletions

diff --git a/org.eclipse.jgit/resources/org/eclipse/jgit/JGitText.properties b/org.eclipse.jgit/resources/org/eclipse/jgit/JGitText.properties
index 133dd17bad..a80e6bcae5 100644
--- a/org.eclipse.jgit/resources/org/eclipse/jgit/JGitText.properties
+++ b/org.eclipse.jgit/resources/org/eclipse/jgit/JGitText.properties
@@ -413,6 +413,7 @@ shortSkipOfBlock=Short skip of block.
 signingNotSupportedOnTag=Signing isn't supported on tag operations yet.
 similarityScoreMustBeWithinBounds=Similarity score must be between 0 and 100.
 sizeExceeds2GB=Path {0} size {1} exceeds 2 GiB limit.
+skipMustBeNonNegative=skip must be >= 0
 smartHTTPPushDisabled=smart HTTP push disabled
 sourceDestinationMustMatch=Source/Destination must match.
 sourceIsNotAWildcard=Source is not a wildcard.
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/JGitText.java b/org.eclipse.jgit/src/org/eclipse/jgit/JGitText.java
index 34c372867c..f4de487558 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/JGitText.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/JGitText.java
@@ -473,6 +473,7 @@ public class JGitText extends TranslationBundle {
 	/***/ public String signingNotSupportedOnTag;
 	/***/ public String similarityScoreMustBeWithinBounds;
 	/***/ public String sizeExceeds2GB;
+	/***/ public String skipMustBeNonNegative;
 	/***/ public String smartHTTPPushDisabled;
 	/***/ public String sourceDestinationMustMatch;
 	/***/ public String sourceIsNotAWildcard;
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/api/LogCommand.java b/org.eclipse.jgit/src/org/eclipse/jgit/api/LogCommand.java
index 632b5d0e30..21a0d342a9 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/api/LogCommand.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/api/LogCommand.java
@@ -59,7 +59,9 @@ import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.revwalk.RevCommit;
 import org.eclipse.jgit.revwalk.RevWalk;
+import org.eclipse.jgit.revwalk.filter.AndRevFilter;
 import org.eclipse.jgit.revwalk.filter.MaxCountRevFilter;
+import org.eclipse.jgit.revwalk.filter.SkipRevFilter;
 import org.eclipse.jgit.treewalk.filter.AndTreeFilter;
 import org.eclipse.jgit.treewalk.filter.PathFilter;
 import org.eclipse.jgit.treewalk.filter.PathFilterGroup;
@@ -88,6 +90,8 @@ public class LogCommand extends GitCommand<Iterable<RevCommit>> {
 
 	private int maxCount = -1;
 
+	private int skip = -1;
+
 	/**
 	 * @param repo
 	 */
@@ -111,7 +115,12 @@ public class LogCommand extends GitCommand<Iterable<RevCommit>> {
 		if (pathFilters.size() > 0)
 			walk.setTreeFilter(AndTreeFilter.create(
 					PathFilterGroup.create(pathFilters), TreeFilter.ANY_DIFF));
-		if (maxCount > -1)
+		if (skip > -1 && maxCount > -1)
+			walk.setRevFilter(AndRevFilter.create(SkipRevFilter.create(skip),
+					MaxCountRevFilter.create(maxCount)));
+		else if (skip > -1)
+			walk.setRevFilter(SkipRevFilter.create(skip));
+		else if (maxCount > -1)
 			walk.setRevFilter(MaxCountRevFilter.create(maxCount));
 		if (!startSpecified) {
 			try {
@@ -253,7 +262,20 @@ public class LogCommand extends GitCommand<Iterable<RevCommit>> {
 	}
 
 	/**
-	 * Limit the number of commits to output
+	 * Skip the number of commits before starting to show the commit output.
+	 *
+	 * @param skip
+	 *            the number of commits to skip
+	 * @return {@code this}
+	 */
+	public LogCommand setSkip(int skip) {
+		checkCallable();
+		this.skip = skip;
+		return this;
+	}
+
+	/**
+	 * Limit the number of commits to output.
 	 *
 	 * @param maxCount
 	 *            the limit
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/filter/SkipRevFilter.java b/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/filter/SkipRevFilter.java
new file mode 100644
index 0000000000..7555fefcc8
--- /dev/null
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/filter/SkipRevFilter.java
@@ -0,0 +1,94 @@
+/*
+ * Copyright (C) 2011, Tomasz Zarna <Tomasz.Zarna@pl.ibm.com>
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+package org.eclipse.jgit.revwalk.filter;
+
+import java.io.IOException;
+
+import org.eclipse.jgit.JGitText;
+import org.eclipse.jgit.errors.IncorrectObjectTypeException;
+import org.eclipse.jgit.errors.MissingObjectException;
+import org.eclipse.jgit.errors.StopWalkException;
+import org.eclipse.jgit.revwalk.RevCommit;
+import org.eclipse.jgit.revwalk.RevWalk;
+
+/**
+ * Filter that includes commits after a configured number are skipped.
+ */
+public class SkipRevFilter extends RevFilter {
+
+	private final int skip;
+
+	private int count;
+
+	/**
+	 * Create a new skip filter.
+	 *
+	 * @param skip
+	 *            the number of commits to skip
+	 * @return a new filter
+	 */
+	public static RevFilter create(int skip) {
+		if (skip < 0)
+			throw new IllegalArgumentException(
+					JGitText.get().skipMustBeNonNegative);
+		return new SkipRevFilter(skip);
+	}
+
+	private SkipRevFilter(int skip) {
+		this.skip = skip;
+	}
+
+	@Override
+	public boolean include(RevWalk walker, RevCommit cmit)
+			throws StopWalkException, MissingObjectException,
+			IncorrectObjectTypeException, IOException {
+		if (skip > count++)
+			return false;
+		return true;
+	}
+
+	@Override
+	public RevFilter clone() {
+		return new SkipRevFilter(skip);
+	}
+}
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