tests/test-conflict

localrepo._tag: add a seek before writing the new tag

Some systems require a seek (or flush) between read and write
operations on the same file object.

This should fix issue838.

#!/bin/sh

hg init
echo "nothing" > a
hg add a
hg commit -m ancestor -d "1000000 0"
echo "something" > a
hg commit -m branch1 -d "1000000 0"
hg co 0
echo "something else" > a
hg commit -m branch2 -d "1000000 0"
hg merge 1
hg id
cat a
hg status