2 files changed, 48 insertions, 1 deletions

diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsReftableDatabase.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsReftableDatabase.java
index 87983ce8c0..6050c15992 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsReftableDatabase.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsReftableDatabase.java
@@ -47,8 +47,10 @@ import java.io.IOException;
 import java.util.Arrays;
 import java.util.ArrayList;
 import java.util.Collections;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 import java.util.concurrent.locks.ReentrantLock;
 
 import org.eclipse.jgit.annotations.Nullable;
@@ -277,6 +279,25 @@ public class DfsReftableDatabase extends DfsRefDatabase {
 
 	/** {@inheritDoc} */
 	@Override
+	public Set<Ref> getTipsWithSha1(ObjectId id) throws IOException {
+		if (!getReftableConfig().isIndexObjects()) {
+			return super.getTipsWithSha1(id);
+		}
+		lock.lock();
+		try {
+			RefCursor cursor = reader().byObjectId(id);
+			Set<Ref> refs = new HashSet<>();
+			while (cursor.next()) {
+				refs.add(cursor.getRef());
+			}
+			return refs;
+		} finally {
+			lock.unlock();
+		}
+	}
+
+	/** {@inheritDoc} */
+	@Override
 	public Ref peel(Ref ref) throws IOException {
 		Ref oldLeaf = ref.getLeaf();
 		if (oldLeaf.isPeeled() || oldLeaf.getObjectId() == null) {
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/lib/RefDatabase.java b/org.eclipse.jgit/src/org/eclipse/jgit/lib/RefDatabase.java
index 877792097c..4d9450e758 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/lib/RefDatabase.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/lib/RefDatabase.java
@@ -44,6 +44,7 @@
 package org.eclipse.jgit.lib;
 
 import static java.util.stream.Collectors.toList;
+import static java.util.stream.Collectors.toSet;
 
 import java.io.IOException;
 import java.util.ArrayList;
@@ -52,7 +53,7 @@ import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
-
+import java.util.Set;
 import org.eclipse.jgit.annotations.NonNull;
 import org.eclipse.jgit.annotations.Nullable;
 
@@ -470,6 +471,31 @@ public abstract class RefDatabase {
 		return Collections.unmodifiableList(result);
 	}
 
+
+	/**
+	 * Returns all refs that resolve directly to the given {@link ObjectId}.
+	 * Includes peeled {@linkObjectId}s. This is the inverse lookup of
+	 * {@link #exactRef(String...)}.
+	 *
+	 * <p>
+	 * The default implementation uses a linear scan. Implementors of
+	 * {@link RefDatabase} should override this method directly if a better
+	 * implementation is possible.
+	 *
+	 * @param id
+	 *            {@link ObjectId} to resolve
+	 * @return a {@link Set} of {@link Ref}s whose tips point to the provided
+	 *         id.
+	 * @throws java.io.IOException
+	 *             the reference space cannot be accessed.
+	 * @since 5.4
+	 */
+	@NonNull
+	public Set<Ref> getTipsWithSha1(ObjectId id) throws IOException {
+		return getRefs().stream().filter(r -> id.equals(r.getObjectId())
+				|| id.equals(r.getPeeledObjectId())).collect(toSet());
+	}
+
 	/**
 	 * Check if any refs exist in the ref database.
 	 * <p>