Correct optimization from 3464f5e77f34; add a test. If there are two (or more) heads that point to the same .hgtags node, we can safely skip parsing the file in all but the last head. (In 3464f5e77f34, we were parsing the file in the first head and skipping all the others.)

#!/bin/sh

echo "[extensions]" >> $HGRCPATH
echo "mq=" >> $HGRCPATH

hg init a
cd a
hg qnew first.patch
hg qnew first.patch

touch ../first.patch
hg qimport ../first.patch

exit 0