Remove Repository.toFile(ObjectId)

Not every type of Repository will be able to map an ObjectId into
a local file system path that stores that object's file contents.
Heck, its not even true for the FileRepository, as an object can
be stored in a pack file and not in its loose format.

Remove this from our public API, it was a mistake to publish it.

Change-Id: I20d1b8c39104023936e6d46a5b0d7ef39ff118e8
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/T0003_Basic.java

@@ -365,8 +365,10 @@ public class T0003_Basic extends SampleDataRepositoryTestCase {
 		assertEquals(cmtid, c.getCommitId());
 
 		// Verify the commit we just wrote is in the correct format.
-		final XInputStream xis = new XInputStream(new FileInputStream(db
-				.toFile(cmtid)));
+		ObjectDatabase odb = db.getObjectDatabase();
+		assertTrue("is ObjectDirectory", odb instanceof ObjectDirectory);
+		final XInputStream xis = new XInputStream(new FileInputStream(
+				((ObjectDirectory) odb).fileFor(cmtid)));
 		try {
 			assertEquals(0x78, xis.readUInt8());
 			assertEquals(0x9c, xis.readUInt8());

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

@@ -380,20 +380,6 @@ public class FileRepository extends Repository {
 		return repoConfig;
 	}
 
-	/**
-	 * Construct a filename where the loose object having a specified SHA-1
-	 * should be stored. If the object is stored in a shared repository the path
-	 * to the alternative repo will be returned. If the object is not yet store
-	 * a usable path in this repo will be returned. It is assumed that callers
-	 * will look for objects in a pack first.
-	 *
-	 * @param objectId
-	 * @return suggested file name
-	 */
-	public File toFile(final AnyObjectId objectId) {
-		return objectDatabase.fileFor(objectId);
-	}
-
 	/**
 	 * Objects known to exist but not expressed by {@link #getAllRefs()}.
 	 * <p>

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

@@ -173,18 +173,6 @@ public abstract class Repository {
 		return fs;
 	}
 
-	/**
-	 * Construct a filename where the loose object having a specified SHA-1
-	 * should be stored. If the object is stored in a shared repository the path
-	 * to the alternative repo will be returned. If the object is not yet store
-	 * a usable path in this repo will be returned. It is assumed that callers
-	 * will look for objects in a pack first.
-	 *
-	 * @param objectId
-	 * @return suggested file name
-	 */
-	public abstract File toFile(AnyObjectId objectId);
-
 	/**
 	 * @param objectId
 	 * @return true if the specified object is stored in this repo or any of the