man 5 hgrc implied you need to use external tools to do CRLF translation.
This is no longer true; win32text provides a much better in-process alternative.
#!/bin/sh
"$TESTDIR/hghave" svn svn-bindings || exit 80
fix_path()
{
tr '\\' /
}
echo "[extensions]" >> $HGRCPATH
echo "convert = " >> $HGRCPATH
svnpath=`pwd`/svn-repo
svnadmin create $svnpath
cat > $svnpath/hooks/pre-revprop-change <<'EOF'
#!/bin/sh
REPOS="$1"
REV="$2"
USER="$3"
PROPNAME="$4"
ACTION="$5"
if [ "$ACTION" = "M" -a "$PROPNAME" = "svn:log" ]; then exit 0; fi
if [ "$ACTION" = "A" -a "$PROPNAME" = "hg:convert-branch" ]; then exit 0; fi
if [ "$ACTION" = "A" -a "$PROPNAME" = "hg:convert-rev" ]; then exit 0; fi
echo "Changing prohibited revision property" >&2
exit 1
EOF
chmod +x $svnpath/hooks/pre-revprop-change
svnurl=file://$svnpath
svn co $svnurl $svnpath-wc
cd $svnpath-wc
echo a > a
svn add a
svn ci -m'added a' a
cd ..
echo % initial roundtrip
hg convert -s svn -d hg $svnpath-wc $svnpath-hg | grep -v initializing
hg convert -s hg -d svn $svnpath-hg $svnpath-wc
echo % second roundtrip should do nothing
hg convert -s svn -d hg $svnpath-wc $svnpath-hg
hg convert -s hg -d svn $svnpath-hg $svnpath-wc
echo % new hg rev
hg clone $svnpath-hg $svnpath-work
echo b > $svnpath-work/b
hg --cwd $svnpath-work add b
hg --cwd $svnpath-work ci -mb
echo % echo hg to svn
hg --cwd $svnpath-hg pull -q $svnpath-work
hg convert -s hg -d svn $svnpath-hg $svnpath-wc
echo % svn back to hg should do nothing
hg convert -s svn -d hg $svnpath-wc $svnpath-hg
echo % hg back to svn should do nothing
hg convert -s hg -d svn $svnpath-hg $svnpath-wc