CommitGraphWriter: Unnest generation-number progress

The ProgressMonitor task to track the calculation of generation
numbers is nested inside the task that follows the writing of all
lines in the commit-graph. ProgressMonitor doesn't support nested
tasks and this confuses the counting.

Move the start/end of the "writing commit graph" task to the
writeCommitData section, after calculating the generation
numbers. Make that task track by commits instead of by lines.

Moving the start/end of the progress task to the chunk-writing
functions is clearer and easier to extend.

Logging of GC before:
Writing out commit-graph in 3 passes:  51% ( 9807/19358)
Computing commit-graph generation numbers: 100% (9551/9551)

Logging of GC after:
Computing commit-graph generation numbers: 100% (9551/9551)
Writing out commit-graph: 100% (9551/9551)

Change-Id: I87d69c06c9a3c7e75be12b6f0d1a63b5924e298a

org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/commitgraph/CommitGraphWriterTest.java

@@ -14,6 +14,7 @@
 import static org.hamcrest.Matchers.containsInAnyOrder;
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 
 import java.io.ByteArrayOutputStream;
@@ -31,6 +32,7 @@
 import org.eclipse.jgit.lib.ConfigConstants;
 import org.eclipse.jgit.lib.NullProgressMonitor;
 import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.lib.ProgressMonitor;
 import org.eclipse.jgit.revwalk.RevBlob;
 import org.eclipse.jgit.revwalk.RevCommit;
 import org.eclipse.jgit.revwalk.RevWalk;
@@ -135,6 +137,56 @@ public void testWriterWithoutExtraEdgeList() throws Exception {
 				NB.decodeInt32(data, 56));
 	}
 
+	@Test
+	public void testProgressMonitor() throws Exception {
+		RevCommit root = commit();
+		RevCommit a = commit(root);
+		RevCommit b = commit(root);
+		RevCommit tip = commit(a, b);
+		Set<ObjectId> wants = Collections.singleton(tip);
+
+		NonNestedTasksProgressMonitor nonNested = new NonNestedTasksProgressMonitor();
+		GraphCommits graphCommits = GraphCommits.fromWalk(nonNested, wants,
+				walk);
+		writer = new CommitGraphWriter(graphCommits, true);
+		writer.write(nonNested, os);
+	}
+
+	private static class NonNestedTasksProgressMonitor
+			implements ProgressMonitor {
+
+		boolean inTask;
+
+		@Override
+		public void start(int totalTasks) {
+		}
+
+		@Override
+		public void beginTask(String title, int totalWork) {
+			assertFalse("Previous monitoring task is not closed", inTask);
+			inTask = true;
+		}
+
+		@Override
+		public void update(int completed) {
+		}
+
+		@Override
+		public void endTask() {
+			assertTrue("Closing task that wasn't started", inTask);
+			inTask = false;
+		}
+
+		@Override
+		public boolean isCancelled() {
+			return false;
+		}
+
+		@Override
+		public void showDuration(boolean enabled) {
+		}
+	}
+
 	static HashSet<String> changedPathStrings(byte[] data) {
 		int oidf_offset = -1;
 		int bidx_offset = -1;

org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties

@@ -886,7 +886,7 @@ writerAlreadyInitialized=Writer already initialized
 writeTimedOut=Write timed out after {0} ms
 writingNotPermitted=Writing not permitted
 writingNotSupported=Writing {0} not supported.
-writingOutCommitGraph=Writing out commit-graph in {0} passes
+writingOutCommitGraph=Writing out commit-graph
 writingObjects=Writing objects
 wrongDecompressedLength=wrong decompressed length
 wrongRepositoryState=Wrong Repository State: {0}

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/commitgraph/CommitGraphWriter.java

@@ -31,7 +31,6 @@
 import java.io.InterruptedIOException;
 import java.io.OutputStream;
 import java.nio.ByteBuffer;
-import java.text.MessageFormat;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashSet;
@@ -131,13 +130,6 @@ public Stats write(@NonNull ProgressMonitor monitor,
 		chunks = Collections.unmodifiableList(chunks);
 
 		long expectedSize = calculateExpectedSize(chunks);
-		long writeCount = 256L + 2 * graphCommits.size()
-				+ graphCommits.getExtraEdgeCnt();
-		monitor.beginTask(
-				MessageFormat.format(JGitText.get().writingOutCommitGraph,
-						Integer.valueOf(chunks.size())),
-				(int) writeCount);
-
 		try (CancellableDigestOutputStream out = new CancellableDigestOutputStream(
 				monitor, commitGraphStream)) {
 			writeHeader(out, chunks.size());
@@ -153,8 +145,6 @@ public Stats write(@NonNull ProgressMonitor monitor,
 		} catch (InterruptedIOException e) {
 			throw new IOException(JGitText.get().commitGraphWritingCancelled,
 					e);
-		} finally {
-			monitor.endTask();
 		}
 		return Stats.from(bloomFilterChunks);
 	}
@@ -290,6 +280,8 @@ private void writeOidLookUp(CancellableDigestOutputStream out)
 	private void writeCommitData(ProgressMonitor monitor,
 			CancellableDigestOutputStream out) throws IOException {
 		int[] generations = computeGenerationNumbers(monitor);
+		monitor.beginTask(JGitText.get().writingOutCommitGraph,
+				graphCommits.size());
 		int num = 0;
 		byte[] tmp = new byte[hashsz + COMMIT_DATA_WIDTH];
 		int i = 0;
@@ -330,6 +322,7 @@ private void writeCommitData(ProgressMonitor monitor,
 			out.getWriteMonitor().update(1);
 			i++;
 		}
+		monitor.endTask();
 	}
 
 	private int[] computeGenerationNumbers(ProgressMonitor monitor)