RevCommitCG: Read changed-path-filters directly from commit graph

RevCommit and RevCommitCG were designed like "pointers" to data that
load the content on demand, not on construction. This saves memory.

Make the loading of changed-path-filter follow the same pattern. The
ChangedPathFilters are only pointers to locations in the commit-graph
(not the actual data), so the memory saving is not that big, but this
is more consistent with the rest of the API.

As 6.7 is not released, we can still change the RevWalk API.

Change-Id: Id4186ea744b8a2418d0329facae69f785108d356

5 files changed, 25 insertions, 28 deletions

diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/commitgraph/CommitGraphWriter.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/commitgraph/CommitGraphWriter.java
index 9d1c33959f..c5cfe95864 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/commitgraph/CommitGraphWriter.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/commitgraph/CommitGraphWriter.java
@@ -48,6 +48,7 @@ import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.ObjectReader;
 import org.eclipse.jgit.lib.ProgressMonitor;
 import org.eclipse.jgit.revwalk.RevCommit;
+import org.eclipse.jgit.revwalk.RevWalk;
 import org.eclipse.jgit.treewalk.EmptyTreeIterator;
 import org.eclipse.jgit.treewalk.TreeWalk;
 import org.eclipse.jgit.util.NB;
@@ -405,25 +406,27 @@ public class CommitGraphWriter {
 		data.write(scratch);
 		int dataHeaderSize = data.size();
 
-		for (RevCommit cmit : graphCommits) {
-			ChangedPathFilter cpf = cmit.getChangedPathFilter();
-			if (cpf != null) {
-				stats.changedPathFiltersReused++;
-			} else {
-				stats.changedPathFiltersComputed++;
-				Optional<HashSet<ByteBuffer>> paths = computeBloomFilterPaths(
-						graphCommits.getObjectReader(), cmit);
-				if (paths.isEmpty()) {
-					cpf = ChangedPathFilter.FULL;
+		try (RevWalk rw = new RevWalk(graphCommits.getObjectReader())) {
+			for (RevCommit cmit : graphCommits) {
+				ChangedPathFilter cpf = cmit.getChangedPathFilter(rw);
+				if (cpf != null) {
+					stats.changedPathFiltersReused++;
 				} else {
-					cpf = ChangedPathFilter.fromPaths(paths.get());
+					stats.changedPathFiltersComputed++;
+					Optional<HashSet<ByteBuffer>> paths = computeBloomFilterPaths(
+							graphCommits.getObjectReader(), cmit);
+					if (paths.isEmpty()) {
+						cpf = ChangedPathFilter.FULL;
+					} else {
+						cpf = ChangedPathFilter.fromPaths(paths.get());
+					}
 				}
+				cpf.writeTo(data);
+				NB.encodeInt32(scratch, 0, data.size() - dataHeaderSize);
+				index.write(scratch);
 			}
-			cpf.writeTo(data);
-			NB.encodeInt32(scratch, 0, data.size() - dataHeaderSize);
-			index.write(scratch);
+			return new BloomFilterChunks(index, data);
 		}
-		return new BloomFilterChunks(index, data);
 	}
 
 	private void writeExtraEdges(CancellableDigestOutputStream out)
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/RevCommit.java b/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/RevCommit.java
index e0bdf3eaf9..4619938147 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/RevCommit.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/RevCommit.java
@@ -694,10 +694,11 @@ public class RevCommit extends RevObject {
 	 * commit graph file, or the commit graph file was generated without changed
 	 * path filters.
 	 *
+	 * @param rw A revwalk to load the commit graph (if available)
 	 * @return the changed path filter
 	 * @since 6.7
 	 */
-	public ChangedPathFilter getChangedPathFilter() {
+	public ChangedPathFilter getChangedPathFilter(RevWalk rw) {
 		return null;
 	}
 
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/RevCommitCG.java b/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/RevCommitCG.java
index 8c8100320a..c7a03992b7 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/RevCommitCG.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/RevCommitCG.java
@@ -30,8 +30,6 @@ class RevCommitCG extends RevCommit {
 
 	private final int graphPosition;
 
-	private final ChangedPathFilter changedPathFilter;
-
 	private int generation = Constants.COMMIT_GENERATION_UNKNOWN;
 
 	/**
@@ -41,14 +39,10 @@ class RevCommitCG extends RevCommit {
 	 *            object name for the commit.
 	 * @param graphPosition
 	 *            the position in the commit-graph of the object.
-	 * @param changedPathFilter
-	 *            the changed path filter if one exists
 	 */
-	protected RevCommitCG(AnyObjectId id, int graphPosition,
-			ChangedPathFilter changedPathFilter) {
+	protected RevCommitCG(AnyObjectId id, int graphPosition) {
 		super(id);
 		this.graphPosition = graphPosition;
-		this.changedPathFilter = changedPathFilter;
 	}
 
 	@Override
@@ -110,7 +104,7 @@ class RevCommitCG extends RevCommit {
 
 	/** {@inheritDoc} */
 	@Override
-	public ChangedPathFilter getChangedPathFilter() {
-		return changedPathFilter;
+	public ChangedPathFilter getChangedPathFilter(RevWalk rw) {
+		return rw.commitGraph().getChangedPathFilter(graphPosition);
 	}
 }
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/RevWalk.java b/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/RevWalk.java
index f4bf710ed2..27a09f4956 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/RevWalk.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/RevWalk.java
@@ -1713,8 +1713,7 @@ public class RevWalk implements Iterable<RevCommit>, AutoCloseable {
 
 	private RevCommit createCommit(AnyObjectId id, int graphPos) {
 		if (graphPos >= 0) {
-			return new RevCommitCG(id, graphPos,
-					commitGraph().getChangedPathFilter(graphPos));
+			return new RevCommitCG(id, graphPos);
 		}
 		return new RevCommit(id);
 	}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/TreeRevFilter.java b/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/TreeRevFilter.java
index f8b11200a7..43571a6868 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/TreeRevFilter.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/TreeRevFilter.java
@@ -133,7 +133,7 @@ public class TreeRevFilter extends RevFilter {
 			int chgs = 0, adds = 0;
 			boolean changedPathFilterUsed = false;
 			boolean mustCalculateChgs = true;
-			ChangedPathFilter cpf = c.getChangedPathFilter();
+			ChangedPathFilter cpf = c.getChangedPathFilter(walker);
 			if (cpf != null) {
 				Optional<Set<byte[]>> paths = pathFilter.getFilter()
 						.getPathsBestEffort();