Memoir: removing headrule in chapter page

Question

How to remove headrule in chapter page without remove of footrule, eg, rule only in foot page in all pages, but without on chapter page, but headrule in others pages.

\documentclass[a4paper]{memoir}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}

\copypagestyle{rgstyle}{headings}
\makeoddhead{rgstyle}{}{}{\slshape\rightmark}
\makeevenhead{rgstyle}{\slshape\leftmark}{}{}
\makeoddfoot{rgstyle}{R\'egis $\smiley$ \the\year}{}{\thepage}
\makeevenfoot{rgstyle}{\thepage}{}{R\'egis $\smiley$ \the\year}
% add line
\makeheadrule{headings}{\textwidth}{\normalrulethickness}
\makefootrule{headings}{\textwidth}{\normalrulethickness}{\footruleskip}
% fix plain
\copypagestyle{plain}{rgstyle} % overwrite plain with rgstyle
\makeoddhead{plain}{}{}{} % remove right header
\makeevenhead{plain}{}{}{} % remove left header
\pagestyle{rgstyle}

\begin{document}

\chapter{Memoir without headrule in chapter page}

\lipsum

\end{document}

Answer 1

memoir, just like book, typesets the first page of \chapter using the plain page style. You must therefore reset the plain page style header rule after copying rgstyle into plain:

\copypagestyle{plain}{rgstyle} % overwrite plain with rgstyle
\makeheadrule{plain}{0pt}{0pt} % remove plain header rule

The second parameter to \makeheadrule{plain}{<len>}{0pt} could just as well have been anything less than \textwidth.