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I wrote my own little source forge using svnkit 1.7 and the DAVServlet.
But recently after upgrading to TortoiseSVN 1.8 checkouts gave me an error because of the Content-Length -1 change I think.
So I tried upgrading the svnkit.jar to 1.8.10 but then I got an error like this:
Unexpected HTTP status 400 'Bad Request' on 'repos/JPAGen/!svn/vcc/default'
I noticed the missing start slash so I wrote a tcp tunnel that injected the slash and that worked almost but gave me another error later where a repo path was still incorrect in some WebDAV XML.
I almost gave up at that point thinking about reverting to TortoiseSVN 1.7 simply.
But I did want to report the problem here so I tried a pure 1.8.10 DAVServlet test to be able to report the issue and that suddenly worked. I used TestSVNKIT as my project name and my context path.
Then I tried to change the context path to "" (an empty string) in the Eclipse module configuration dialog (to be able to access the web project without the need for a path in the URL) just as I do for my source forge project.
And boom, same error.
So I grepped the svnkit-dav code for getContextPath and there was only one important location: