git clone http://scm.trinitydesktop.org/scm/git/tdelibs
     pushd tdelibs
         git submodule init
         git submodule update
         git checkout v3.5.13
     popd


Results in the following errors

Submodule path 'libltdl': checked out 
'6d6796c294ca6e9b7f83c295217817c4bf486031'
error: The following untracked working tree files would be overwritten 
by checkout:
         libltdl/CMakeLists.txt
         libltdl/COPYING.LIB
         libltdl/Makefile.am
         libltdl/README
         libltdl/ltdl.c
         libltdl/ltdl.h
         libltdl/ltdl.m4
         libltdl/ltdl_win.c
         libltdl/ltdl_win.h
Please move or remove them before you can switch branches.