I'm using Cygwin. I assumed that git would use the first svn client it finds on the path, but that doesn't seem to be the case:
$ type svn
svn is /cygdrive/c/Program Files/SlikSvn/bin/svn
$ echo $PATH | sed 's/:/\n/g'
/cygdrive/c/Program Files/SlikSvn/bin
/bin
/home/me/bin
/home/me/bin
/usr/local/bin
/usr/bin
/cygdrive/c/Program Files (x86)/Haskell/bin
/cygdrive/c/Program Files (x86)/Haskell Platform/2012.4.0.0/lib/extralibs/bin
/cygdrive/c/Program Files (x86)/Haskell Platform/2012.4.0.0/bin
/cygdrive/c/Windows/system32
/cygdrive/c/Windows
/cygdrive/c/Windows/System32/Wbem
/cygdrive/c/Windows/System32/WindowsPowerShell/v1.0
/cygdrive/c/Program Files/TortoiseSVN/bin
/cygdrive/c/Program Files/Java/jdk1.6.0_34/bin
/cygdrive/c/apache-maven-3.0.4/bin
/cygdrive/c/apache-ant-1.8.0/bin
/cygdrive/c/Program Files (x86)/Haskell Platform/2012.4.0.0/mingw/bin
/cygdrive/c/cygwin/bin
/cygdrive/c/Program Files (x86)/QuickTime/QTSystem
/cygdrive/c/Program Files/nodejs
/cygdrive/c/Program Files (x86)/phantomjs-1.9.1-windows
/cygdrive/c/Program Files/SlikSvn/bin
$ git svn dcommit
Committing to https://svn.corp.corp.com/svn/results/trunk ...
R foo => bar
assertion "svn_fspath__is_canonical(child_fspath)" failed: file "/usr/src/subversion/subversion-1.8.5-1/src/subversion-1.8.5/subversion/libsvn_subr/dirent_uri.c", line 2504, function: svn_fspath__skip_ancestor
error: git-svn died of signal 6
The reason I don't think it's using the first on one the path is because the error mentions /usr/src/subversion/subversion-1.8.5-1/src/subversion-1.8.5/subversion/libsvn_subr/dirent_uri.c
and the first on my path is at /cygdrive/c/Program Files/SlikSvn/bin
.