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 -e
umask 027
mkdir test1
cd test1
hg init
touch a b
hg add a b
hg ci -m "added a b" -d "1000000 0"
cd ..
hg clone test1 test3
mkdir test2
cd test2
hg init
hg pull ../test1
hg co
chmod +x a
hg ci -m "chmod +x a" -d "1000000 0"
cd ../test1
echo 123 >>a
hg ci -m "a updated" -d "1000000 0"
hg pull ../test2
hg heads
hg history
hg -v merge
cd ../test3
echo 123 >>b
hg ci -m "b updated" -d "1000000 0"
hg pull ../test2
hg heads
hg history
hg -v merge
ls -l ../test[123]/a > foo
cut -b 1-10 < foo
hg debugindex .hg/data/a.i
hg debugindex ../test2/.hg/data/a.i
hg debugindex ../test1/.hg/data/a.i