rhg: allow setting defaults.cmd to an empty string This is used by at least one hg UI to prevent defaults from affecting the command: https://github.com/emacs-mirror/emacs/blob/b71beb7ae7c60a5c5af608420d28fdda5265a264/lisp/vc/vc-hg.el#L245 Let's let it work.

uncommit: migrate `opts` to native kwargs

split: migrate `opts` to native kwargs

releasenotes: migrate `opts` to native kwargs

narrow: hoist a variable to a higher level to avoid use-before-init warning In practice, this shouldn't generate an IOError, so there wouldn't have been a problem. But PyCharm didn't know that.

narrow: migrate `opts` to native kwargs

largefiles: migrate `opts` to native kwargs

keyword: migrate `opts` to native kwargs

gpg: use a context manager to write `.hgsigs`

gpg: migrate `opts` to native kwargs