Set environment variable DOCS_RS when building crates (#852)

Author: ldm0

src/docbuilder/rustwide_builder.rs

@@ -516,6 +516,9 @@ impl RustwideBuilder {
                         .unwrap_or_default(),
                 )
                 .env("RUSTDOCFLAGS", rustdoc_flags.join(" "))
+                // For docs.rs detection from build script:
+                // https://github.com/rust-lang/docs.rs/issues/147
+                .env("DOCS_RS", "1")
                 .args(&cargo_args)
                 .run()
                 .is_ok()

tera-templates/core/about.html

@@ -28,6 +28,12 @@ <h1 id="crate-title">About Docs.rs</h1>
             {%- endif -%}
         </p>
 
+        <p>
+            Docs.rs builds crates with environment variable <code>DOCS_RS</code> set to
+            <code>1</code>, which enables the crate to detect docs.rs and build the
+            crate differently for docs.
+        </p>
+
         <p>
             The source code of Docs.rs is available on
             <a href="{{ docsrs_repo }}">GitHub</a>. If