This may relate to issue904.

I have a server running on embedded MIPS hardware[0].  It is
non-trivial for me to get a statically-linked darcs binary for this
architecture, particularly since the OS is using µclibc rather than
GNU libc.

Therefore, I have installed an sftp server and used sshfs to mount the
remote filesystem on my Debian laptop.  I then tried using "darcs get"
to copy a repository to the remote system.  Here is the transcript:

    $ sshfs -o idmap=user ymir.twb.ath.cx:/srv/www /tmp/www
    $ darcs get --repodir /tmp/www/Preferences ~/Preferences
    darcs: _darcs/hashed_inventory-0: renameFile: permission denied (Operation not permitted)

Data gathering:

    $ darcs --version
    2.1.0 (release)
    $ sshfs --version
    SSHFS version 2.1
    FUSE library version: 2.7.4
    fusermount version: 2.7.4
    using FUSE kernel interface version 7.8
    $ ssh ymir.twb.ath.cx uname -a
    Linux Ymir 2.4.34 #13 Thu Jul 26 17:55:20 CEST 2007 mips unknown
    $ ssh ymir.twb.ath.cx "ipkg list_installed | grep sftp"
    openssh-sftp-server - 4.5p1-1 -
    $

[0] an Asus WL-500gP running http://openwrt.org/ Kamkikaze 7.07.

Turns out I need to tell sshfs to work around suckage.  I managed to
appease darcs by adding "rename" to the list of workarounds.

$ sshfs -o intr,idmap=user,workaround=rename:buflimit ymir.twb.ath.cx:/srv/www /tmp/www
$ darcs get --repodir /tmp/www/test2 /home/twb/Preferences
darcs: takeLock /tmp/www/test2/_darcs/lock in /tmp/www/test2: atomic_create /tmp/www/test2/_darcs/lock in /tmp/www/test2: unsupported operation (Function not implemented)
$ rm -rf /tmp/www/test2
$ DARCS_SLOPPY_LOCKS=Yes darcs get --repodir /tmp/www/test2 /home/twb/Preferences
Finished getting.