Use 5 MiB for RevWalk default limit

Instead of getting the limit from CoreConfig, use the larger of the
reader's limit or 5 MiB, under the assumption that any annotated tag
or commit of interest should be under 5 MiB.  But if a repository
was really insane and had bigger objects, the reader implementation
can set its streaming limit higher in order to allow RevWalk to
still process it.

Change-Id: If2c15235daa3e2d1f7167e781aa83fedb5af9a30
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

org.eclipse.jgit/src/org/eclipse/jgit/lib/CoreConfig.java

@@ -47,7 +47,6 @@
 package org.eclipse.jgit.lib;
 
 import static java.util.zip.Deflater.DEFAULT_COMPRESSION;
-import static org.eclipse.jgit.lib.ObjectLoader.STREAM_THRESHOLD;
 
 import org.eclipse.jgit.lib.Config.SectionParser;
 
@@ -68,21 +67,12 @@ public class CoreConfig {
 
 	private final boolean logAllRefUpdates;
 
-	private final int streamFileThreshold;
-
 	private final boolean autoCRLF;
 
 	private CoreConfig(final Config rc) {
 		compression = rc.getInt("core", "compression", DEFAULT_COMPRESSION);
 		packIndexVersion = rc.getInt("pack", "indexversion", 2);
 		logAllRefUpdates = rc.getBoolean("core", "logallrefupdates", true);
-
-		long maxMem = Runtime.getRuntime().maxMemory();
-		long sft = rc.getLong("core", null, "streamfilethreshold", STREAM_THRESHOLD);
-		sft = Math.min(sft, maxMem / 4); // don't use more than 1/4 of the heap
-		sft = Math.min(sft, Integer.MAX_VALUE); // cannot exceed array length
-		streamFileThreshold = (int) sft;
-
 		autoCRLF = rc.getBoolean("core", "autocrlf", false);
 	}
 
@@ -108,11 +98,6 @@ public class CoreConfig {
 		return logAllRefUpdates;
 	}
 
-	/** @return the size threshold beyond which objects must be streamed. */
-	public int getStreamFileThreshold() {
-		return streamFileThreshold;
-	}
-
 	/**
 	 * @return whether automatic CRLF conversion has been configured
 	 */

org.eclipse.jgit/src/org/eclipse/jgit/revwalk/RevWalk.java

@@ -61,7 +61,6 @@ import org.eclipse.jgit.errors.RevWalkException;
 import org.eclipse.jgit.lib.AnyObjectId;
 import org.eclipse.jgit.lib.AsyncObjectLoaderQueue;
 import org.eclipse.jgit.lib.Constants;
-import org.eclipse.jgit.lib.CoreConfig;
 import org.eclipse.jgit.lib.MutableObjectId;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.ObjectIdSubclassMap;
@@ -96,6 +95,8 @@ import org.eclipse.jgit.treewalk.filter.TreeFilter;
  * {@link #next()} does not.
  */
 public class RevWalk implements Iterable<RevCommit> {
+	private static final int MB = 1 << 20;
+
 	/**
 	 * Set on objects whose important header data has been loaded.
 	 * <p>
@@ -171,9 +172,6 @@ public class RevWalk implements Iterable<RevCommit> {
 
 	private final ObjectIdSubclassMap<RevObject> objects;
 
-	/** Largest commit or annotated tag we are willing to touch. */
-	private final int bigFileThreshold;
-
 	private int freeFlags = APP_FLAGS;
 
 	private int delayFreeFlags;
@@ -230,13 +228,6 @@ public class RevWalk implements Iterable<RevCommit> {
 		filter = RevFilter.ALL;
 		treeFilter = TreeFilter.ALL;
 		retainBody = true;
-
-		if (repo != null) {
-			CoreConfig cfg = repo.getConfig().get(CoreConfig.KEY);
-			bigFileThreshold = cfg.getStreamFileThreshold();
-		} else {
-			bigFileThreshold = 15 * 1024 * 1024;
-		}
 	}
 
 	/** @return the reader this walker is using to load objects. */
@@ -867,7 +858,7 @@ public class RevWalk implements Iterable<RevCommit> {
 	byte[] getCachedBytes(RevObject obj, ObjectLoader ldr)
 			throws LargeObjectException, MissingObjectException, IOException {
 		try {
-			return ldr.getCachedBytes(bigFileThreshold);
+			return ldr.getCachedBytes(5 * MB);
 		} catch (LargeObjectException tooBig) {
 			tooBig.setObjectId(obj);
 			throw tooBig;