gc: loosen unreferenced objects

An unreferenced object might appear in a pack.  This could only happen
because it was previously referenced, and then later that reference
was removed.  When we gc, we copy the referenced objects into a new
pack, and delete the old pack.  This would remove the unreferenced
object.  Now we first create a loose object from any unreferenced
object in the doomed pack.  This kicks off the two-week grace period
for that object, after which it will be collected if it's not
referenced.

This matches the behavior of regular git.

Change-Id: I59539aca1d0d83622c41aa9bfbdd72fa868ee9fb
Signed-off-by: David Turner <dturner@twosigma.com>
Signed-off-by: Jonathan Nieder <jrn@google.com>

1 files changed, 19 insertions, 4 deletions

diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/GcBasicPackingTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/GcBasicPackingTest.java
index 8a9ad89600..c7e5973f3f 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/GcBasicPackingTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/GcBasicPackingTest.java
@@ -55,6 +55,7 @@ import java.util.Date;
 import java.util.List;
 
 import org.eclipse.jgit.junit.TestRepository.BranchBuilder;
+import org.eclipse.jgit.lib.RefUpdate;
 import org.eclipse.jgit.revwalk.RevCommit;
 import org.eclipse.jgit.storage.pack.PackConfig;
 import org.junit.Test;
@@ -188,16 +189,26 @@ public class GcBasicPackingTest extends GcTestCase {
 		BranchBuilder bb = tr.branch("refs/heads/master");
 		bb.commit().message("M").add("M", "M").create();
 
+		String tempRef = "refs/heads/soon-to-be-unreferenced";
+		BranchBuilder bb2 = tr.branch(tempRef);
+		bb2.commit().message("M").add("M", "M").create();
+
 		gc.setExpireAgeMillis(0);
 		gc.gc();
 		stats = gc.getStatistics();
 		assertEquals(0, stats.numberOfLooseObjects);
-		assertEquals(3, stats.numberOfPackedObjects);
+		assertEquals(4, stats.numberOfPackedObjects);
 		assertEquals(1, stats.numberOfPackFiles);
 		File oldPackfile = tr.getRepository().getObjectDatabase().getPacks()
 				.iterator().next().getPackFile();
 
 		fsTick();
+
+		// delete the temp ref, orphaning its commit
+		RefUpdate update = tr.getRepository().getRefDatabase().newUpdate(tempRef, false);
+		update.setForceUpdate(true);
+		update.delete();
+
 		bb.commit().message("B").add("B", "Q").create();
 
 		// The old packfile is too young to be deleted. We should end up with
@@ -208,7 +219,7 @@ public class GcBasicPackingTest extends GcTestCase {
 		assertEquals(0, stats.numberOfLooseObjects);
 		// if objects exist in multiple packFiles then they are counted multiple
 		// times
-		assertEquals(9, stats.numberOfPackedObjects);
+		assertEquals(10, stats.numberOfPackedObjects);
 		assertEquals(2, stats.numberOfPackFiles);
 
 		// repack again but now without a grace period for loose objects. Since
@@ -219,15 +230,19 @@ public class GcBasicPackingTest extends GcTestCase {
 		assertEquals(0, stats.numberOfLooseObjects);
 		// if objects exist in multiple packFiles then they are counted multiple
 		// times
-		assertEquals(9, stats.numberOfPackedObjects);
+		assertEquals(10, stats.numberOfPackedObjects);
 		assertEquals(2, stats.numberOfPackFiles);
 
 		// repack again but now without a grace period for packfiles. We should
 		// end up with one packfile
 		gc.setPackExpireAgeMillis(0);
+
+		// we want to keep newly-loosened objects though
+		gc.setExpireAgeMillis(-1);
+
 		gc.gc();
 		stats = gc.getStatistics();
-		assertEquals(0, stats.numberOfLooseObjects);
+		assertEquals(1, stats.numberOfLooseObjects);
 		// if objects exist in multiple packFiles then they are counted multiple
 		// times
 		assertEquals(6, stats.numberOfPackedObjects);