`vanc` skips over latex commands if they have an optional argument containing a space

[alexandreroberts]

Example, using vimtex for text object definitions:

This \emph{is} a \cite[23 note 3]{command} even though it cites a page. This one does not \cite{citekey} a page.

Begin at the beginning of the line. vanc<ESC> jumps to the end of \emph{is}, but then doing vanc<ESC> again jumps to the second cite command, \cite{citekey}.

I don't think this is a problem with vimtex's definition of the command text object, since it correctly highlights the first cite command as such (though perhaps the highlighting and the text object definitions are separate in vimtex?).