message: strip blank line from examples in <pre>
  There is a special parsing rule for the <pre> tag itself which forces to
  ignore the leading line breaks to be removed[1]. But it does not work on a
  nested <code> tag.
  [1]:
diff: <p>
  To recognize Docs.rs from <code>build.rs</code> files, you can test for the environment variable <code>DOCS_RS</code>, e.g.:
  {% filter dedent(levels=4) -%}
  - <pre><code class="lang-rust">
  - if let Ok(_) = std::env::var("DOCS_RS") {
  + <pre><code class="lang-rust">if let Ok(_) = std::env::var("DOCS_RS") {
  // ... your code here ...
  - }
  - </code></pre>
  + }</code></pre>
  {%- endfilter %}
  This approach can be helpful if you need dependencies for building the library, but not for building the documentation.
  </p>
  <p>
  You can configure how your crate is built by adding <a href="metadata">package metadata</a> to your <code>Cargo.toml</code>, e.g.:
  {% filter dedent -%}
  - <pre><code class="lang-toml">
  - [package.metadata.docs.rs]
  - rustc-args = ["--cfg", "docsrs"]
  - </code></pre>
  + <pre><code class="lang-toml">[package.metadata.docs.rs]
  + rustc-args = ["--cfg", "docsrs"]</code></pre>
  {%- endfilter %}
  Here, the compiler arguments are set so that <code>#[cfg(docsrs)]</code> (not to be confused with <code>#[cfg(doc)]</code>) can be used for conditional compilation.
  This approach is also useful for setting <a href="https://doc.rust-lang.org/cargo/reference/features.html">cargo features</a>.
  