I’m no expert on this, my friend said that this is due to there is no guarantee that apr_file_rename() will success on different devices.
Based on the discussion here I was able to create a patch.
If you use FreeBSD ports, simply put the patch in
/usr/ports/devel/subversion/files/, The port system will automatically apply this patch before build.
I have only tested this patch on Subversion 1.7.5 !