RefTreeDatabase: Expose bootstrap refs in getAdditionalRefs

By showing the bootstrap layer in getAdditionalRefs() garbage
collector code can be more RefDatabase agnostic and not care about
the special case of RefTree and RefTreeNames for the purposes of
building up the roots to GC. Instead they can combine getRefs(ALL)
and getAdditionalRefs() and have a clean set of roots.

Change-Id: I665cd2456e9316640215b6a08bc728d1356f36d8

org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/reftree/RefTreeDatabaseTest.java

@@ -124,6 +124,17 @@ public class RefTreeDatabaseTest {
 		assertTrue("no references", refdb.getRefs(ALL).isEmpty());
 		assertTrue("no references", refdb.getRefs(R_HEADS).isEmpty());
 		assertTrue("no references", refdb.getRefs(R_TAGS).isEmpty());
+		assertTrue("no references", refdb.getAdditionalRefs().isEmpty());
+	}
+
+	@Test
+	public void testGetAdditionalRefs() throws IOException {
+		update("refs/heads/master", A);
+
+		List<Ref> addl = refdb.getAdditionalRefs();
+		assertEquals(1, addl.size());
+		assertEquals("refs/txn/committed", addl.get(0).getName());
+		assertEquals(getTxnCommitted(), addl.get(0).getObjectId());
 	}
 
 	@Test

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsGarbageCollector.java

@@ -194,7 +194,7 @@ public class DfsGarbageCollector {
 			refdb.refresh();
 			objdb.clearCache();
 
-			Collection<Ref> refsBefore = RefTreeNames.allRefs(refdb);
+			Collection<Ref> refsBefore = getAllRefs();
 			packsBefore = packsToRebuild();
 			if (packsBefore.isEmpty())
 				return true;
@@ -235,6 +235,18 @@ public class DfsGarbageCollector {
 		}
 	}
 
+	private Collection<Ref> getAllRefs() throws IOException {
+		Collection<Ref> refs = refdb.getRefs(RefDatabase.ALL).values();
+		List<Ref> addl = refdb.getAdditionalRefs();
+		if (!addl.isEmpty()) {
+			List<Ref> all = new ArrayList<>(refs.size() + addl.size());
+			all.addAll(refs);
+			all.addAll(addl);
+			return all;
+		}
+		return refs;
+	}
+
 	private List<DfsPackFile> packsToRebuild() throws IOException {
 		DfsPackFile[] packs = objdb.getPacks();
 		List<DfsPackFile> out = new ArrayList<DfsPackFile>(packs.length);

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/GC.java

@@ -629,15 +629,16 @@ public class GC {
 	}
 
 	/**
-	 * Returns a map of all refs and additional refs (e.g. FETCH_HEAD,
+	 * Returns a collection of all refs and additional refs (e.g. FETCH_HEAD,
 	 * MERGE_HEAD, ...)
 	 *
-	 * @return a map where names of refs point to ref objects
+	 * @return a collection of refs pointing to live objects.
 	 * @throws IOException
 	 */
 	private Collection<Ref> getAllRefs() throws IOException {
-		Collection<Ref> refs = RefTreeNames.allRefs(repo.getRefDatabase());
-		List<Ref> addl = repo.getRefDatabase().getAdditionalRefs();
+		RefDatabase refdb = repo.getRefDatabase();
+		Collection<Ref> refs = refdb.getRefs(RefDatabase.ALL).values();
+		List<Ref> addl = refdb.getAdditionalRefs();
 		if (!addl.isEmpty()) {
 			List<Ref> all = new ArrayList<>(refs.size() + addl.size());
 			all.addAll(refs);

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftree/RefTreeDatabase.java

@@ -47,6 +47,8 @@ import static org.eclipse.jgit.lib.Ref.Storage.LOOSE;
 import static org.eclipse.jgit.lib.Ref.Storage.PACKED;
 
 import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
@@ -250,7 +252,23 @@ public class RefTreeDatabase extends RefDatabase {
 
 	@Override
 	public List<Ref> getAdditionalRefs() throws IOException {
-		return Collections.emptyList();
+		Collection<Ref> txnRefs;
+		if (txnNamespace != null) {
+			txnRefs = bootstrap.getRefs(txnNamespace).values();
+		} else {
+			Ref r = bootstrap.exactRef(txnCommitted);
+			if (r != null && r.getObjectId() != null) {
+				txnRefs = Collections.singleton(r);
+			} else {
+				txnRefs = Collections.emptyList();
+			}
+		}
+
+		List<Ref> otherRefs = bootstrap.getAdditionalRefs();
+		List<Ref> all = new ArrayList<>(txnRefs.size() + otherRefs.size());
+		all.addAll(txnRefs);
+		all.addAll(otherRefs);
+		return all;
 	}
 
 	@Override

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftree/RefTreeNames.java

@@ -43,14 +43,6 @@
 
 package org.eclipse.jgit.internal.storage.reftree;
 
-import static org.eclipse.jgit.lib.RefDatabase.ALL;
-
-import java.io.IOException;
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.List;
-
-import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.lib.RefDatabase;
 
 /** Magic reference name logic for RefTrees. */
@@ -92,33 +84,6 @@ public class RefTreeNames {
 		return false;
 	}
 
-	/**
-	 * Snapshot all references from a RefTreeDatabase and its bootstrap.
-	 * <p>
-	 * There may be name conflicts with multiple {@link Ref} objects containing
-	 * the same name in the returned collection.
-	 *
-	 * @param refdb
-	 *            database instance.
-	 * @return all known references.
-	 * @throws IOException
-	 *             references cannot be enumerated.
-	 */
-	public static Collection<Ref> allRefs(RefDatabase refdb)
-			throws IOException {
-		Collection<Ref> refs = refdb.getRefs(ALL).values();
-		if (!(refdb instanceof RefTreeDatabase)) {
-			return refs;
-		}
-
-		RefDatabase bootstrap = ((RefTreeDatabase) refdb).getBootstrap();
-		Collection<Ref> br = bootstrap.getRefs(ALL).values();
-		List<Ref> all = new ArrayList<>(refs.size() + br.size());
-		all.addAll(refs);
-		all.addAll(br);
-		return all;
-	}
-
 	private RefTreeNames() {
 	}
 }