### Please describe the problem.

With the upgrade to git-annex 6.20170925 I can no longer copy files to box via webdav. I notice that the changelog suggests that there were many changes to the webdav backend, including a new path for temporary files and url-escaping of file names. I have been using webdav + Box successfully for almost two years. My box/webdav backed was set up with chunking and encryption:

     WEBDAV_USERNAME=[username] WEBDAV_PASSWORD=[passwd] git annex initremote box type=webdav url=https://dav.box.com/dav/mystuff/annex chunk=100mb keyid=[keyid]

Now when I try to add and copy a file to webdav I get the following error:

     (checking box...)                         
     DAV failure: Status {statusCode = 405, statusMessage = "Method Not Allowed"} "<?xml version=\"1.0\" encoding=\"utf-8\"?>\n<d:error xmlns:d=\"DAV:\" 
     xmlns:s=\"http://sabredav.org/ns\">\n  <s:exception>Sabre_DAV_Exception_MethodNotAllowed</s:exception>\n  <s:message>The resource you tried to create 
     already exists</s:message>\n</d:error>\n"
     CallStack (from HasCallStack):     
     error, called at ./Remote/WebDAV.hs:381:78 in main:Remote.WebDAV failed            
     (recording state in git...)      

### What steps will reproduce the problem?

Add a file to an annex repo with a webdav backend set up per the settings above:
    
     git add test.pdf

Attempt to copy that file to the webdav backend:

     git-annex copy -t box test.pdf

### What version of git-annex are you using? On what operating system?

OS = arch linux (Linux archbook 4.12.13-1-ARCH #1 SMP PREEMPT Fri Sep 15 06:36:43 UTC 2017 x86_64 GNU/Linux)

git annex version =

     git-annex version: 6.20170925-g76c9b580b
     build flags: Assistant Webapp Pairing Testsuite S3(multipartupload)(storageclasses) WebDAV Inotify DBus DesktopNotify ConcurrentOutput TorrentParser MagicMime Feeds Quvi
     dependency versions: aws-0.16 bloomfilter-2.0.1.0 cryptonite-0.24 DAV-1.3.1 feed-1.0.0.0 ghc-8.2.1 http-client-0.5.7.0 persistent-sqlite-2.6.2 torrent-10000.1.1 uuid-1.3.13 yesod-1.4.5
     key/value backends: SHA256E SHA256 SHA512E SHA512 SHA224E SHA224 SHA384E SHA384 SHA3_256E SHA3_256 SHA3_512E SHA3_512 SHA3_224E SHA3_224 SHA3_384E SHA3_384 SKEIN256E SKEIN256 SKEIN512E SKEIN512 SHA1E SHA1 MD5E MD5 WORM URL
     remote types: git gcrypt p2p S3 bup directory rsync web bittorrent webdav tahoe glacier ddar hook external
     local repository version: unknown
     supported repository versions: 3 5 6
     upgrade supported from repository versions: 0 1 2 3 4 5
     operating system: linux x86_64

### Have you had any luck using git-annex before? (Sometimes we get tired of reading bug reports all day and a lil' positive end note does wonders)

Yes! A huge word of thanks for this amazing software! Since I work on multiple linux boxes, git annex keeps track of all my big files and enables me to move them back and forth with minimal fuss.

> [[done]]; seems this is fixed. --[[Joey]]
