dirstate: explicitly write the dirstate after `keyword` "overwrite"

I am working on making the dirstate write patterns more predictable. This patch is
part of a small series of similar patches that adds a explicit dirstate write in
a handful of location where the dirstate is updated "a bit in a strange way".

With this explicit write, we are no longer relying on implicite write of the
dirstate on `wlock` release. This make the world a better place.

hgext/keyword.py

@@ -442,6 +442,7 b' def _kwfwrite(ui, repo, expand, *pats, *'
         if status.modified or status.added or status.removed or status.deleted:
             raise error.Abort(_(b'outstanding uncommitted changes'))
         kwt.overwrite(wctx, status.clean, True, expand)
+        repo.dirstate.write(repo.currenttransaction())
 
 
 @command(