If you want to get the revision number and use that as part of the filename (or UI text) for the setup you are generating you have to use compile-time commands like !system
and !searchparse
...
Edit:
!tempfile StdOut
!echo "${StdOut}"
!system '"svn" info c:\foo\trunk > "${stdout}"'
!searchparse /file "${StdOut}" "Revision: " SVNREV
!delfile "${StdOut}"
!undef StdOut
Name "MyApp SVN.${SVNREV}"