pw.preparePack(pm, want, have);
if (pw.getObjectCount() == 0)
return null;
// create temporary files
String id = pw.computeName().getName();
File packdir = new File(repo.getObjectsDirectory(), "pack"); //$NON-NLS-1$
tmpPack = File.createTempFile("gc_", ".pack_tmp", packdir); //$NON-NLS-1$ //$NON-NLS-2$
tmpIdx = new File(packdir, tmpPack.getName().substring(0,
tmpPack.getName().lastIndexOf('.'))
+ ".idx_tmp"); //$NON-NLS-1$