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
echo '[Section]' >> $HGRCPATH
echo 'KeY = Case Sensitive' >> $HGRCPATH
echo 'key = lower case' >> $HGRCPATH
hg showconfig Section