We have upgraded our SVN server from 1.7.14 to 1.8.13 and suddenly we can longer commit over HTTP. The HTTP clients are behind a proxy but the proxy configuration has not changed. On the server side we get the following error in the apache log 192.168.24.10 - user [24/Apr/2015:12:25:24 +0200] "MERGE /repo/trunk HTTP/1.1" 400 299 Error code 400 is "bad request". No further information is given on why mod_dav_svn suddenly considers the MERGE request as a bad request.
Original issue reported by skratky