fix!: work around Pandoc 3.2+ breaking links to chapters (#100)

Pandoc used to wrap the contents of each file in a div when
`--file-scope` was used, which `mdbook-pandoc` relied on to link to the
start of a chapter. This behavior was removed in
jgm/pandoc@30442b7,
which was released in version 3.2.

To work around this, `mdbook-pandoc` now searches for the first heading
in each chapter and, if present, links to this heading as a proxy for
the beginning of the chapter. This should make sense in most cases,
since mdBook chapters tend to start with a top-level heading, but will
result in regressions if chapters don't contain any headings or the
headings they do contain don't have a usable identifier (this is the
case with [punctuation-only
headings](https://doc.rust-lang.org/rust-by-example/std/result/question_mark.html),
for instance). See the [Pandoc
manual](https://pandoc.org/MANUAL.html#extension-gfm_auto_identifiers)
for the algorithm used to generate identifiers for headings.

Closes #99

README.md

@@ -118,8 +118,8 @@ variable-name = "value"
 
 ### Known Issues
 
-- When rendering to PDF through LaTeX, links to chapters sometimes link to slightly before the beginning of the chapter.
-  See: https://github.com/jgm/pandoc/issues/9200
+- Linking to a chapter does not work unless the chapter contains a heading with a non-empty identifier (either auto-generated or explicitly specified).
+  See: https://github.com/max-heller/mdbook-pandoc/pull/100
 
 ### Comparison to alternatives
 

scripts/install-ci-deps

@@ -9,9 +9,9 @@ sudo apt-get update
 curl -LsSf https://get.nexte.st/0.9/linux | tar zxf - -C ${CARGO_HOME:-~/.cargo}/bin
 
 # Pandoc
-curl -LsSf https://github.com/jgm/pandoc/releases/download/3.1.12.3/pandoc-3.1.12.3-linux-amd64.tar.gz | tar zxf -
-echo "$PWD/pandoc-3.1.12.3/bin" >> $GITHUB_PATH
-export PATH="$PWD/pandoc-3.1.12.3/bin:$PATH"
+curl -LsSf https://github.com/jgm/pandoc/releases/download/3.2/pandoc-3.2-linux-amd64.tar.gz | tar zxf -
+echo "$PWD/pandoc-3.2/bin" >> $GITHUB_PATH
+export PATH="$PWD/pandoc-3.2/bin:$PATH"
 
 # rsvg-convert (SVG support)
 sudo apt-get install -y librsvg2-bin