Ssh

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* SFTPFile.prefetch() added to dramatically speed up downloads (automatically
turned on in SFTPClient.get())
* fixed bug where garbage-collected Channels could trigger the Transport to
close the session (reported by gordon good)
* fixed a deadlock in rekeying (reported by wendell wood)
* fixed some windows bugs and SFTPAttributes.__str__() (reported by grzegorz
makarewicz)
* better sftp error reporting by adding fake "errno" info to IOErrors

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* added support for "keyboard-interactive" authentication
* added mode (on by default) where password authentication will try to
fallback to "keyboard-interactive" if it's supported
* added pipelining to SFTPFile.write and SFTPClient.put
* fixed bug with SFTPFile.close() not guarding against being called more
than once (thanks to Nathaniel Smith)
* fixed broken 'a' flag in SFTPClient.file() (thanks to Nathaniel Smith)
* fixed up epydocs to look nicer
* reorganized auth_transport into auth_handler, which seems to be a cleaner
separation
* demo scripts fixed to have a better chance of loading the host keys
correctly on windows/cygwin

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* added SSH-agent support (for posix) from john rochester
* added chdir() and getcwd() to SFTPClient, to emulate a "working directory"
* added get() and put() to SFTPClient, to emulate ftp whole-file transfers
* added check() to SFTPFile (a file hashing protocol extension)
* fixed Channels and SFTPFiles (among others) to auto-close when GC'd
* fixed Channel.fileno() for Windows, this time really
* don't log socket errors as "unknown exception"
* some misc. backward-compatible API improvements (like allowing
Transport.start_client() and start_server() to be called in a blocking way)

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* added SFTPClient.close()
* fixed up some outdated documentation
* made SFTPClient.file() an alias for open()
* added Transport.open_sftp_client() for convenience
* refactored packetizing out of Transport
* fixed bug (reported by alain s.) where connecting to a non-SSH host could
cause ssh to freeze up
* fixed Channel.fileno() for Windows (again)
* some more unit tests

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* fixed a bug where packets larger than about 12KB would cause the session
to die on all platforms except osx
* added a potential workaround for windows to let Channel.fileno() (and
therefore the select module) work!
* changed API for subsystem handlers (sorry!) to pass more info and make it
easier to write a functional SFTP server

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* added SFTPClient.listdir_attr() for fetching a list of files and their
attributes in one call
* added Channel.recv_exit_status() and Channel.send_exit_status() for
manipulating the exit status of a command from either client or server
mode
* moved check_global_request into ServerInterface, where it should've been
all along (oops)
* SFTPHandle's default implementations are fleshed out more
* made logging a bit more consistent, and started logging thread ids
* fixed a few race conditions, one of which would sometimes cause a Transport
to fail to start on slow machines
* more unit tests