convert: avoid svn log retrieval process cleanup
With huge history (like kdelibs), the process termination suddenly consumes a
lot of memory (from 700M to 1.3G+). Since the job is done, clean termination is
not required, just exit.
hg init test
cd test
echo foo > a
hg ci -Ama
hg up -r0000
echo bar > a
echo % should issue warning
hg ci -Amb
hg up -r0000
echo stuffy > a
echo % should not issue warning
hg ci -q -Amc
hg up -r0000
echo crap > a
hg branch testing
echo % should not issue warning
hg ci -q -Amd