Add a new singlePack option to PackConfig

If set, "singlePack" will create a single GC pack file for all
objects reachable from refs/*. If not set, the GC pack will contain
object reachable from refs/heads/* and refs/tags/*, and the GC_REST
pack will contain all other reachable objects.

Change-Id: I56bcb6a9da2c10a0909c2f940c025db6f3acebcb
Signed-off-by: Terry Parker <tparker@google.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/DfsGarbageCollectorTest.java

@@ -31,6 +31,7 @@ import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
 
+/** Tests for pack creation and garbage expiration. */
 public class DfsGarbageCollectorTest {
 	private TestRepository<InMemoryRepository> git;
 	private InMemoryRepository repo;
@@ -632,6 +633,26 @@ public class DfsGarbageCollectorTest {
 		}
 	}
 
+	@Test
+	public void testSinglePackForAllRefs() throws Exception {
+		RevCommit commit0 = commit().message("0").create();
+		git.update("head", commit0);
+		RevCommit commit1 = commit().message("1").parent(commit0).create();
+		git.update("refs/notes/note1", commit1);
+
+		DfsGarbageCollector gc = new DfsGarbageCollector(repo);
+		gc.setGarbageTtl(0, TimeUnit.MILLISECONDS);
+		gc.getPackConfig().setSinglePack(true);
+		run(gc);
+		assertEquals(1, odb.getPacks().length);
+
+		gc = new DfsGarbageCollector(repo);
+		gc.setGarbageTtl(0, TimeUnit.MILLISECONDS);
+		gc.getPackConfig().setSinglePack(false);
+		run(gc);
+		assertEquals(2, odb.getPacks().length);
+	}
+
 	private TestRepository<InMemoryRepository>.CommitBuilder commit() {
 		return git.commit();
 	}

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

@@ -274,6 +274,12 @@ public class DfsGarbageCollector {
 			// Hoist all branch tips and tags earlier in the pack file
 			tagTargets.addAll(allHeadsAndTags);
 
+			// Combine the GC_REST objects into the GC pack if requested
+			if (packConfig.getSinglePack()) {
+				allHeadsAndTags.addAll(nonHeads);
+				nonHeads.clear();
+			}
+
 			boolean rollback = true;
 			try {
 				packHeads(pm);

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

@@ -865,6 +865,12 @@ public class GC {
 		tagTargets.addAll(allHeadsAndTags);
 		nonHeads.addAll(indexObjects);
 
+		// Combine the GC_REST objects into the GC pack if requested
+		if (pconfig != null && pconfig.getSinglePack()) {
+			allHeadsAndTags.addAll(nonHeads);
+			nonHeads.clear();
+		}
+
 		List<PackFile> ret = new ArrayList<>(2);
 		PackFile heads = null;
 		if (!allHeadsAndTags.isEmpty()) {

org.eclipse.jgit/src/org/eclipse/jgit/storage/pack/PackConfig.java

@@ -260,6 +260,8 @@ public class PackConfig {
 
 	private boolean cutDeltaChains;
 
+	private boolean singlePack;
+
 	/** Create a default configuration. */
 	public PackConfig() {
 		// Fields are initialized to defaults.
@@ -320,6 +322,7 @@ public class PackConfig {
 		this.bitmapExcessiveBranchCount = cfg.bitmapExcessiveBranchCount;
 		this.bitmapInactiveBranchAgeInDays = cfg.bitmapInactiveBranchAgeInDays;
 		this.cutDeltaChains = cfg.cutDeltaChains;
+		this.singlePack = cfg.singlePack;
 	}
 
 	/**
@@ -554,6 +557,30 @@ public class PackConfig {
 		cutDeltaChains = cut;
 	}
 
+	/**
+	 * @return true if all of refs/* should be packed in a single pack. Default
+	 *        is false, packing a separate GC_REST pack for references outside
+	 *        of refs/heads/* and refs/tags/*.
+	 * @since 4.9
+	 */
+	public boolean getSinglePack() {
+		return singlePack;
+	}
+
+	/**
+	 * If {@code true}, packs a single GC pack for all objects reachable from
+	 * refs/*. Otherwise packs the GC pack with objects reachable from
+	 * refs/heads/* and refs/tags/*, and a GC_REST pack with the remaining
+	 * reachable objects. Disabled by default, packing GC and GC_REST.
+	 *
+	 * @param single
+	 *            true to pack a single GC pack rather than GC and GC_REST packs
+	 * @since 4.9
+	 */
+	public void setSinglePack(boolean single) {
+		singlePack = single;
+	}
+
 	/**
 	 * Get the number of objects to try when looking for a delta base.
 	 *
@@ -1026,6 +1053,8 @@ public class PackConfig {
 				rc.getBoolean("pack", "deltacompression", isDeltaCompress())); //$NON-NLS-1$ //$NON-NLS-2$
 		setCutDeltaChains(
 				rc.getBoolean("pack", "cutdeltachains", getCutDeltaChains())); //$NON-NLS-1$ //$NON-NLS-2$
+		setSinglePack(
+				rc.getBoolean("pack", "singlepack", getSinglePack())); //$NON-NLS-1$ //$NON-NLS-2$
 		setBuildBitmaps(
 				rc.getBoolean("pack", "buildbitmaps", isBuildBitmaps())); //$NON-NLS-1$ //$NON-NLS-2$
 		setBitmapContiguousCommitCount(
@@ -1073,6 +1102,7 @@ public class PackConfig {
 				.append(getBitmapExcessiveBranchCount());
 		b.append(", bitmapInactiveBranchAge=") //$NON-NLS-1$
 				.append(getBitmapInactiveBranchAgeInDays());
+		b.append(", singlePack=").append(getSinglePack()); //$NON-NLS-1$
 		return b.toString();
 	}
 }