Configure core.bigFileThreshold into PackWriter

C Git's fast-import uses this to determine the maximum file size
that it tries to delta compress, anything equal to or above this
setting is stored with as a whole object with simple deflate.

Define the configuration so we can use it later.

Change-Id: Iea46e787d019a1b6c51135cc73d7688a02e207f5
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

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

@@ -65,12 +65,15 @@ class PackConfig {
 
 	final int indexVersion;
 
+	final long bigFileThreshold;
+
 	private PackConfig(Config rc) {
 		deltaWindow = rc.getInt("pack", "window", PackWriter.DEFAULT_DELTA_SEARCH_WINDOW_SIZE);
 		deltaWindowMemory = rc.getLong("pack", null, "windowmemory", 0);
 		deltaDepth = rc.getInt("pack", "depth", PackWriter.DEFAULT_MAX_DELTA_DEPTH);
 		compression = compression(rc);
 		indexVersion = rc.getInt("pack", "indexversion", 2);
+		bigFileThreshold = rc.getLong("core", null, "bigfilethreshold", PackWriter.DEFAULT_BIG_FILE_THRESHOLD);
 	}
 
 	private static int compression(Config rc) {

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

@@ -172,6 +172,8 @@ public class PackWriter {
 	 */
 	public static final int DEFAULT_DELTA_SEARCH_WINDOW_SIZE = 10;
 
+	static final long DEFAULT_BIG_FILE_THRESHOLD = 50 * 1024 * 1024;
+
 	private static final int PACK_VERSION_GENERATED = 2;
 
 	@SuppressWarnings("unchecked")
@@ -216,6 +218,8 @@ public class PackWriter {
 
 	private int indexVersion;
 
+	private long bigFileThreshold = DEFAULT_BIG_FILE_THRESHOLD;
+
 	private boolean thin;
 
 	private boolean ignoreMissingUninteresting = true;
@@ -269,6 +273,7 @@ public class PackWriter {
 		maxDeltaDepth = pc.deltaDepth;
 		compressionLevel = pc.compression;
 		indexVersion = pc.indexVersion;
+		bigFileThreshold = pc.bigFileThreshold;
 	}
 
 	private static Config configOf(final Repository repo) {
@@ -455,6 +460,29 @@ public class PackWriter {
 			deltaSearchWindowSize = objectCount;
 	}
 
+	/**
+	 * Get the maximum file size that will be delta compressed.
+	 * <p>
+	 * Files bigger than this setting will not be delta compressed, as they are
+	 * more than likely already highly compressed binary data files that do not
+	 * delta compress well, such as MPEG videos.
+	 *
+	 * @return the configured big file threshold.
+	 */
+	public long getBigFileThreshold() {
+		return bigFileThreshold;
+	}
+
+	/**
+	 * Set the maximum file size that should be considered for deltas.
+	 *
+	 * @param bigFileThreshold
+	 *            the limit, in bytes.
+	 */
+	public void setBigFileThreshold(long bigFileThreshold) {
+		this.bigFileThreshold = bigFileThreshold;
+	}
+
 	/** @return true if this writer is producing a thin pack. */
 	public boolean isThin() {
 		return thin;