RevWalk: Add a setFirstParent that mimics C git's --first-parent

RevWalk does not currently provide a --first-parent equivalent and the
feature has been requested.

Add a field to the RevWalk class to specify whether walks should
traverse first parents only. Modify Generator implementations to support
the feature.

Change-Id: I4a9a0d5767f82141dcf6d08659d7cb77c585fae4
Signed-off-by: Dave Borowitz <dborowitz@google.com>
Signed-off-by: Alex Spradlin <alexaspradlin@google.com>

1 files changed, 16 insertions, 3 deletions

diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/AbstractRevQueue.java b/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/AbstractRevQueue.java
index 247a3bdb28..7b5e6fa310 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/AbstractRevQueue.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/AbstractRevQueue.java
@@ -49,6 +49,10 @@ abstract class AbstractRevQueue extends Generator {
 	/** Current output flags set for this generator instance. */
 	int outputType;
 
+	AbstractRevQueue(boolean firstParent) {
+		super(firstParent);
+	}
+
 	/**
 	 * Add a commit to the queue.
 	 * <p>
@@ -96,10 +100,15 @@ abstract class AbstractRevQueue extends Generator {
 	 */
 	public final void addParents(RevCommit c, RevFlag queueControl) {
 		final RevCommit[] pList = c.parents;
-		if (pList == null)
+		if (pList == null) {
 			return;
-		for (RevCommit p : pList)
-			add(p, queueControl);
+		}
+		for (int i = 0; i < pList.length; i++) {
+			if (firstParent && i > 0) {
+				break;
+			}
+			add(pList[i], queueControl);
+		}
 	}
 
 	/**
@@ -138,6 +147,10 @@ abstract class AbstractRevQueue extends Generator {
 	}
 
 	private static class AlwaysEmptyQueue extends AbstractRevQueue {
+		private AlwaysEmptyQueue() {
+			super(false);
+		}
+
 		@Override
 		public void add(RevCommit c) {
 			throw new UnsupportedOperationException();