RevWalk: new method createReachabilityChecker()

Every caller would need to check if bitmaps are available in the repo to
instantiate a reachability checker.

Offer a method to create the reachability checker in the walk: the
caller has already a walk over the repo, and the walk has all the
information required.

This allows us to make the implementation classes package-private.

Change-Id: I355e47486fcd9d55baa7cb5700ec08dcc230eea5
Signed-off-by: Ivan Frade <ifrade@google.com>

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

@@ -55,10 +55,8 @@ import org.eclipse.jgit.lib.NullProgressMonitor;
 
 /**
  * Checks the reachability using bitmaps.
- *
- * @since 5.4
  */
-public class BitmappedReachabilityChecker implements ReachabilityChecker {
+class BitmappedReachabilityChecker implements ReachabilityChecker {
 
 	private final RevWalk walk;
 

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

@@ -52,10 +52,8 @@ import org.eclipse.jgit.errors.MissingObjectException;
 /**
  * Checks the reachability walking the graph from the starters towards the
  * target.
- *
- * @since 5.4
  */
-public class PedestrianReachabilityChecker implements ReachabilityChecker {
+class PedestrianReachabilityChecker implements ReachabilityChecker {
 
 	private final boolean topoSort;
 

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

@@ -249,6 +249,23 @@ public class RevWalk implements Iterable<RevCommit>, AutoCloseable {
 		return reader;
 	}
 
+	/**
+	 * Get a reachability checker for commits over this revwalk.
+	 *
+	 * @return the most efficient reachability checker for this repository.
+	 * @throws IOException
+	 *             if it cannot open any of the underlying indices.
+	 *
+	 * @since 5.4
+	 */
+	public ReachabilityChecker createReachabilityChecker() throws IOException {
+		if (reader.getBitmapIndex() != null) {
+			return new BitmappedReachabilityChecker(this);
+		}
+
+		return new PedestrianReachabilityChecker(true, this);
+	}
+
 	/**
 	 * {@inheritDoc}
 	 * <p>

org.eclipse.jgit/src/org/eclipse/jgit/transport/UploadPack.java

@@ -106,10 +106,8 @@ import org.eclipse.jgit.lib.RefDatabase;
 import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.revwalk.AsyncRevObjectQueue;
 import org.eclipse.jgit.revwalk.BitmapWalker;
-import org.eclipse.jgit.revwalk.BitmappedReachabilityChecker;
 import org.eclipse.jgit.revwalk.DepthWalk;
 import org.eclipse.jgit.revwalk.ObjectWalk;
-import org.eclipse.jgit.revwalk.PedestrianReachabilityChecker;
 import org.eclipse.jgit.revwalk.ReachabilityChecker;
 import org.eclipse.jgit.revwalk.RevCommit;
 import org.eclipse.jgit.revwalk.RevFlag;
@@ -1909,9 +1907,8 @@ public class UploadPack {
 			}
 
 			// All wants are commits, we can use ReachabilityChecker
-			ReachabilityChecker reachabilityChecker = repoHasBitmaps
+			ReachabilityChecker reachabilityChecker = walk
-					? new BitmappedReachabilityChecker(walk)
+					.createReachabilityChecker();
-					: new PedestrianReachabilityChecker(true, walk);
 
 			List<RevCommit> starters = objectIdsToRevCommits(walk,
 					reachableFrom);