[WebDav] Fix copies that include overwrites for the webdav slave
Fixes https://bugs.kde.org/show_bug.cgi?id=422238
There were a number of different things going on that contributed to this bug (not checking for existing file in some branches, reporting disk space of 0 when the server doesn't specify, etc.). I thus added black box testing for webdav (using https://github.com/mar10/wsgidav/) to improve stability and verify that I didn't break anything. This was modeled of of the ftptest autotest. I'm not sure if I did this in the best way with cmake and all.
Testing:
- Autotest that does black-box style testing using wsgidav.
- Manual testing against both wsgidav and https://www.webdavserver.com/User0e5176f (which uses a java implementation of a webdav server)
Concerns: I'm using ulimit.h to find the maximum value of a qint64. There may be portability issues here.
Edited by Ben Gruber