### Please describe the problem.

Upload to box.com (corporate account so filesizes could be large, chunking to 50MB anyways) WebDAV times out quite frequently... I wonder if annex could try more times etc?


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

6.20170525+gitge1cf095ae-1~ndall+1

### Please provide any additional information below.

[[!format sh """
hopa:/tmp/testbox
$> git annex copy -J4 --to=box-dartm3.com --json --json-progress video.mp4 
...
{"byte-progress":13166304,"action":{"command":"copy","note":"to box-dartm3.com...","key":"MD5E-s1073741824--e06da14afc6face003121641e60593bb.mp4","file":"video.mp4"},"total-size":1073741824,"percent-progress":"1.23%"}
{"command":"copy","note":"checking box-dartm3.com...","success":false,"key":"MD5E-s1073741824--e06da14afc6face003121641e60593bb.mp4","file":"video.mp4"}
  DAV failure: 408 "Request Timeout"
  CallStack (from HasCallStack):
    error, called at ./Remote/WebDAV.hs:324:47 in main:Remote.WebDAV
git-annex: copy: 1 failed

$> git annex copy -J4 --to=box-dartm3.com --json --json-progress video.mp4
{"byte-progress":0,"action":{"command":"copy","note":"to box-dartm3.com...","key":"MD5E-s1073741824--e06da14afc6face003121641e60593bb.mp4","file":"video.mp4"},"total-size":1073741824,"percent-progress":"0%"}
{"byte-progress":32752,"action":{"command":"copy","note":"to box-dartm3.com...","key":"MD5E-s1073741824--e06da14afc6face003121641e60593bb.mp4","file":"video.mp4"},"total-size":1073741824,"percent-progress":"0%"}

...
{"byte-progress":225153536,"action":{"command":"copy","note":"to box-dartm3.com...","key":"MD5E-s1073741824--e06da14afc6face003121641e60593bb.mp4","file":"video.mp4"},"total-size":1073741824,"percent-progress":"20.97%"}
{"command":"copy","note":"checking box-dartm3.com...","success":false,"key":"MD5E-s1073741824--e06da14afc6face003121641e60593bb.mp4","file":"video.mp4"}
  DAV failure: 408 "Request Timeout"
  CallStack (from HasCallStack):
    error, called at ./Remote/WebDAV.hs:324:47 in main:Remote.WebDAV
git-annex: copy: 1 failed

$> git annex copy -J4 --to=box-dartm3.com --json --json-progress video.mp4
{"byte-progress":200000000,"action":{"command":"copy","note":"to box-dartm3.com...","key":"MD5E-s1073741824--e06da14afc6face003121641e60593bb.mp4","file":"video.mp4"},"total-size":1073741824,"percent-progress":"18.63%"}
...

"""]]

apparently it is actually timing out on checking (I guess after chunk completion?), not even when copying... could there be multiple attempts and some grace time period for webdav server possibly to "finish receiving" a particular file?


[[!meta author="yoh"]]
