locking: hold the wlock for the full duration of the "keyword demo"

The risk of racing the demo is low, since it seems to create its own repository
on the fly. However it is clearer and more consistent.

hgext/keyword.py

@@ -531,10 +531,10 b' def demo(ui, repo, *args, **opts):'
     demoitems(b'keywordmaps', kwmaps.items())
     keywords = b'$' + b'$\n$'.join(sorted(kwmaps.keys())) + b'$\n'
     repo.wvfs.write(fn, keywords)
+    with repo.wlock():
     repo[None].add([fn])
     ui.note(_(b'\nkeywords written to %s:\n') % fn)
     ui.note(keywords)
-    with repo.wlock():
         repo.dirstate.setbranch(b'demobranch')
     for name, cmd in ui.configitems(b'hooks'):
         if name.split(b'.', 1)[0].find(b'commit') > -1: