[sync] Fix performance problem with GitModelCache#getChildren

The problem was that it returned a child for each changed file, instead
of only the direct children. So e.g. with changes in "dir/a", "dir/b"
and "dir/c", it returned a node for "dir" three times. When the number
of changes is significant, this resulted in many children returned, each
of which also has children which will be processed by the calling code.

The code in GitModelCommit for tree construction did it right. To fix
this, this change consolidates the two tree construction implementations
into one which should be correct.

It also takes care that the final tree nodes use as little memory as
possible by using arrays.

Bug: 396209
Change-Id: I0f139cf7747affb06b32cee584355cf60b46fb76

2 files changed, 33 insertions, 2 deletions

diff --git a/org.eclipse.egit.ui.test/src/org/eclipse/egit/ui/internal/synchronize/model/GitModelCacheTest.java b/org.eclipse.egit.ui.test/src/org/eclipse/egit/ui/internal/synchronize/model/GitModelCacheTest.java
index 66bb5c7fbd..4668849c08 100644
--- a/org.eclipse.egit.ui.test/src/org/eclipse/egit/ui/internal/synchronize/model/GitModelCacheTest.java
+++ b/org.eclipse.egit.ui.test/src/org/eclipse/egit/ui/internal/synchronize/model/GitModelCacheTest.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (C) 2011, Dariusz Luksza <dariusz@luksza.org>
+ * Copyright (C) 2011, 2013 Dariusz Luksza <dariusz@luksza.org> and others.
  *
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
@@ -8,13 +8,20 @@
  *******************************************************************************/
 package org.eclipse.egit.ui.internal.synchronize.model;
 
+import static org.eclipse.jgit.junit.JGitTestUtil.writeTrashFile;
+import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 import static org.mockito.Mockito.mock;
 
 import java.io.File;
+import java.util.Map;
 
+import org.eclipse.egit.core.synchronize.GitCommitsModelCache.Change;
+import org.eclipse.egit.core.synchronize.StagedChangeCache;
 import org.eclipse.egit.ui.Activator;
+import org.eclipse.jgit.api.Git;
+import org.eclipse.jgit.storage.file.FileRepository;
 import org.junit.BeforeClass;
 import org.junit.Test;
 
@@ -93,6 +100,30 @@ public class GitModelCacheTest extends GitModelTestCase {
 		assertFalse(actual);
 	}
 
+	@Test
+	public void shouldReturnChildren() throws Exception {
+		FileRepository repo = lookupRepository(leftRepoFile);
+		writeTrashFile(repo, "dir/a.txt", "trash");
+		writeTrashFile(repo, "dir/b.txt", "trash");
+		writeTrashFile(repo, "dir/c.txt", "trash");
+		writeTrashFile(repo, "dir/d.txt", "trash");
+		new Git(repo).add().addFilepattern("dir").call();
+
+		Map<String, Change> changes = StagedChangeCache.build(repo);
+		assertEquals(4, changes.size());
+
+		GitModelCache cache = new GitModelCache(createModelRepository(), repo,
+				changes);
+
+		GitModelObject[] cacheChildren = cache.getChildren();
+		assertEquals(1, cacheChildren.length);
+		GitModelObject dir = cacheChildren[0];
+		assertEquals("dir", dir.getName());
+
+		GitModelObject[] dirChildren = dir.getChildren();
+		assertEquals(4, dirChildren.length);
+	}
+
 	@BeforeClass public static void setupEnvironment() throws Exception {
 		leftRepoFile = createProjectAndCommitToRepository();
 
diff --git a/org.eclipse.egit.ui.test/src/org/eclipse/egit/ui/internal/synchronize/model/GitModelCacheTreeTest.java b/org.eclipse.egit.ui.test/src/org/eclipse/egit/ui/internal/synchronize/model/GitModelCacheTreeTest.java
index 25aa328033..20f2198e47 100644
--- a/org.eclipse.egit.ui.test/src/org/eclipse/egit/ui/internal/synchronize/model/GitModelCacheTreeTest.java
+++ b/org.eclipse.egit.ui.test/src/org/eclipse/egit/ui/internal/synchronize/model/GitModelCacheTreeTest.java
@@ -15,7 +15,7 @@ import static org.mockito.Mockito.mock;
 import org.eclipse.core.runtime.IPath;
 import org.eclipse.egit.core.synchronize.GitCommitsModelCache.Change;
 import org.eclipse.egit.ui.Activator;
-import org.eclipse.egit.ui.internal.synchronize.model.GitModelCache.FileModelFactory;
+import org.eclipse.egit.ui.internal.synchronize.model.TreeBuilder.FileModelFactory;
 import org.eclipse.jgit.lib.Repository;
 import org.junit.BeforeClass;
 import org.junit.Test;