带有垂直条的引文式环境，跨页面

Question

以下 LaTeX 代码创建了一个类似引号的环境（“答案”），其左侧有一个竖线。如何重新定义该环境，使其跨越分页符？

\documentclass{article}
\usepackage[svgnames]{xcolor}
\usepackage{lipsum}
\usepackage[height=4in]{geometry} % keep pages small for demo

\newsavebox{\mybox}
\newlength{\mydepth}
\newlength{\myheight}
\newenvironment{answer}%
{\vspace*{3pt}\par\begin{lrbox}{\mybox}\quad\begin{minipage}{.89\linewidth}\color{black}\setlength{\parskip}{10pt plus 1pt minus 1pt}\vspace*{-.7\baselineskip}}%
{\vspace*{.3\baselineskip}\end{minipage}\end{lrbox}%
\settodepth{\mydepth}{\usebox{\mybox}}%
\settoheight{\myheight}{\usebox{\mybox}}%
\addtolength{\myheight}{\mydepth}%
\noindent\makebox[0pt]{%
  \color{black}\hspace{-0pt}\rule[-\mydepth]{1pt}{\myheight}}%
  \usebox{\mybox}%
  \vspace*{3pt}}

\begin{document}

\lipsum[1]
  \begin{answer}
    \lipsum[2-3]
  \end{answer}

\end{document}

Answer 1

该changebar计划确实提供了所需的解决方案。

\documentclass{article}
\usepackage{color}
\usepackage{lipsum}
\usepackage[xcolor,leftbars]{changebar}
\usepackage[height=3in]{geometry}

\cbcolor{red}
\newenvironment{answer}%
{\begin{quote}%
  \begin{changebar}\cbcolor{gray}\color{black}}%
  {\end{changebar}%
\end{quote}}

\begin{document}

\lipsum[1]\

\begin{answer}
  \lipsum[2-3]
\end{answer}

\end{document}