localrepo: make _applyrequirements more specific
Localrepo's _applyrequirements function isn't very straightforward about what
it does. Its purpose is to both act as a setter for the requirements attribute,
and to apply appropriate requirements to the opener's configuration.
This change makes the function just focus on the latter responsibility. We
rename it as such, and make setting the requirements attribute the
responsibility of the caller.
Issue351: mq: qrefresh can create extra revlog entry
$ echo "[extensions]" >> $HGRCPATH
$ echo "mq=" >> $HGRCPATH
$ hg init
$ hg qinit
$ echo b > b
$ hg ci -A -m foo
adding b
$ echo cc > b
$ hg qnew -f foo.diff
$ echo b > b
$ hg qrefresh
$ hg debugindex b
rev offset length ..... linkrev nodeid p1 p2 (re)
0 0 3 ..... 0 1e88685f5dde 000000000000 000000000000 (re)