templatekw: use ctx.rev() instead of casting context to int basectx has __int__ implemented. Per mailing list discussion with Yuya, we don't like having this implemented because it is too much magic and in some cases rev() will return None, which isn't an int. So convert a `'%d' % ctx` to ctx.rev() instead. Differential Revision: https://phab.mercurial-scm.org/D2423