I think I have worked around the lifetime issue by keeping references to the intermediate str's.

src/command/build/render.rs

@@ -38,12 +38,20 @@ impl SiteRenderer {
             return Err("Expect exactly 1 main.dust template file.".into());
         }
 
-        for entry in main_template {
-            load_template_from_include_dir(&mut renderer_integration, entry)?;
-        }
+        let decoded_templates = {
+            let mut decoded_templates =
+                Vec::with_capacity(main_template.len() + other_templates.len());
+            for entry in main_template {
+                decoded_templates.push(build_name_contents_pairs(entry)?);
+            }
+            for entry in other_templates {
+                decoded_templates.push(build_name_contents_pairs(entry)?);
+            }
+            decoded_templates
+        };
 
-        for entry in other_templates {
-            load_template_from_include_dir(&mut renderer_integration, entry)?;
+        for (name, contents) in decoded_templates {
+            renderer_integration.load_template(name, contents)?;
         }
 
         for blog_post in &self.blog_posts {
@@ -55,10 +63,9 @@ impl SiteRenderer {
     }
 }
 
-fn load_template_from_include_dir<RI: RendererIntegration>(
-    renderer_integration: &mut RI,
-    entry: &include_dir::File<'_>,
-) -> Result<(), CustomError> {
+fn build_name_contents_pairs<'a>(
+    entry: &'a include_dir::File<'_>,
+) -> Result<(&'a str, &'a str), CustomError> {
     let path = entry.path();
     let name = path
         .file_stem()
@@ -66,6 +73,5 @@ fn load_template_from_include_dir<RI: RendererIntegration>(
         .to_str()
         .ok_or("All template filenames should be valid utf-8.")?;
     let contents = std::str::from_utf8(entry.contents())?;
-    renderer_integration.load_template(name, contents)?;
-    Ok(())
+    Ok((name, contents))
 }