recursive get and recursive put

[zooko]

It would be good if the command-lines

allmydata-tahoe get

and

allmydata-tahoe put

supported the --recursive or -r option so that you could upload or download and entire collection of files with one command-line.

There are actually a host of issues that arise in implementing this, such as those mentioned in the "names versus identifiers" section of webapi.txt, and quoted here:

For example, suppose you are writing code which recursively downloads the
contents of a directory. The first thing your code does is fetch the listing
of the contents of the directory. For each child that it fetched, if that
child is a file then it downloads the file, and if that child is a directory
then it recurses into that directory. Now, if the download and the recurse
actions are performed using the child's name, then the results might be
wrong, because for example a child name that pointed to a sub-directory when
you listed the directory might have been changed to point to a file, in which
case your attempt to recurse into it would result in an error and the file
would be skipped, or a child name that pointed to a file when you listed the
directory might now point to a sub-directory, in which case your attempt to
download the child would result in a file containing HTML text describing the
sub-directory!

These problems can be avoided by traversing identifiers instead of names, but the next problems can't. The next problems are that dirnodes can recurse (a dirnode can contain an entry pointing to another dirnode which contains an entry pointing to the first), or can converge (two entries in the same or different dirnodes can point to the same object). We could implement a recursive download of such things by (perhaps arbitrarily) choosing one path to be a real link and the other to be a symlink. But Windows doesn't have symlinks. Another option would be to abort and print an error message if such a pattern is encountered.