Download pack-*.idx to /tmp if not on local filesystem

If the destination repository doesn't use an ObjectDirectory to
store its objects, we can't download to the object directory.
Instead pull the pack-*.idx files down to temporary files in the
JVM's default temporary directory.

Change-Id: Ied16bc89be624d87110ba42ba52d698a6ea7d982
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

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

@@ -70,6 +70,7 @@ import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.FileMode;
 import org.eclipse.jgit.lib.MutableObjectId;
 import org.eclipse.jgit.lib.ObjectChecker;
+import org.eclipse.jgit.lib.ObjectDirectory;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.PackIndex;
 import org.eclipse.jgit.lib.PackLock;
@@ -240,8 +241,10 @@ class WalkFetchConnection extends BaseFetchConnection {
 
 	@Override
 	public void close() {
-		for (final RemotePack p : unfetchedPacks)
+		for (final RemotePack p : unfetchedPacks) {
+			if (p.tmpIdx != null)
 				p.tmpIdx.delete();
+		}
 		for (final WalkRemoteObjectDatabase r : remotes)
 			r.close();
 	}
@@ -512,6 +515,7 @@ class WalkFetchConnection extends BaseFetchConnection {
 				// it failed the index and pack are unusable and we
 				// shouldn't consult them again.
 				//
+				if (pack.tmpIdx != null)
 					pack.tmpIdx.delete();
 				packItr.remove();
 			}
@@ -788,12 +792,11 @@ class WalkFetchConnection extends BaseFetchConnection {
 
 		final String idxName;
 
-		final File tmpIdx;
+		File tmpIdx;
 
 		PackIndex index;
 
 		RemotePack(final WalkRemoteObjectDatabase c, final String pn) {
-			final File objdir = local.getObjectsDirectory();
 			connection = c;
 			packName = pn;
 			idxName = packName.substring(0, packName.length() - 5) + ".idx";
@@ -803,13 +806,19 @@ class WalkFetchConnection extends BaseFetchConnection {
 				tn = tn.substring(5);
 			if (tn.endsWith(".idx"))
 				tn = tn.substring(0, tn.length() - 4);
-			tmpIdx = new File(objdir, "walk-" + tn + ".walkidx");
+
+			if (local.getObjectDatabase() instanceof ObjectDirectory) {
+				tmpIdx = new File(((ObjectDirectory) local.getObjectDatabase())
+						.getDirectory(), "walk-" + tn + ".walkidx");
+			}
 		}
 
 		void openIndex(final ProgressMonitor pm) throws IOException {
 			if (index != null)
 				return;
-			if (tmpIdx.isFile()) {
+			if (tmpIdx == null)
+				tmpIdx = File.createTempFile("jgit-walk-", ".idx");
+			else if (tmpIdx.isFile()) {
 				try {
 					index = PackIndex.open(tmpIdx);
 					return;