A superb blog article here:

http://alt-tag.com/blog/archives/2006/11/integrating-mantis-and-subversion/

describes how to integrate SVN and Mantis, however the post-commit hook is for linux.  To do this on windows:

post-commit.bat

SET REPOS=%1
SET REV=%2
SET TMP_LOG=%TEMP%.\svnfileTMP-%REV%
D:\<svnhome>\bin\svnlook log -r %REV% %REPOS%>%TMP_LOG% 

D:\<phphome>\php.exe -q D:\<mantishome>\core\checkin.php < %TMP_LOG%