When trying to find a notebook to associate a file with, reinteract seems a little over-zealous.
I placed (admittedly, for debugging purposes) an index.rnb file in my home directory, and tried to open a standalone worksheet in a subdirectory from the command line. The logic in find_notebook_path() chains up to higher-level directories, at which point the index.rnb in ~ caused reinteract to scan my entire home directory, adding everything in it to the file list; this operation also crashed out when it hit a file that it couldn't access, but that's beside the point.
I'm not sure what the correct behaviour here is, but there is obvious potential for the current notebook search method to do bad things. One possibility would be for index.rnb files to store their containing path, only scan that directory on opening, and don't auto-associate with files unless they are under the stored path. In this case there would probably need to be some kind of prompt for when people moved/renamed the containing directory.
