Links inside fig.cap garbled with LaTeX

[jweisber]

Thanks for the terrific package—and for the whole knitrverse!

I wonder if there's a bug that affects links placed inside fig.cap when working with LaTeX (tufte_handout or tufte_book). Here's a MWE:

---
title: "Minimal Working Example"
output: tufte::tufte_handout  # but tufte::tufte_html is fine
---

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```{r fig.cap="A plot of the famous [cars data set](https://stat.ethz.ch/R-manual/R-devel/library/datasets/html/cars.html)."}
plot(cars)
```

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This gives me the result:

Whereas substituting tufte::tufte_html seems to work as expected.

Digging into the generated .tex file, it looks like the problem is the link just hasn't been converted from markdown to LaTeX:

\begin{figure}
\includegraphics{MWE_files/figure-latex/unnamed-chunk-1-1} \caption[A plot of the famous [cars data set](https://stat.ethz.ch/R-manual/R-devel/library/datasets/html/cars.html)]{A plot of the famous [cars data set](https://stat.ethz.ch/R-manual/R-devel/library/datasets/html/cars.html).}\label{fig:unnamed-chunk-1}
\end{figure}