Add option to exclude files from build process

crates/mdbook-core/src/config.rs

@@ -518,6 +518,12 @@ pub struct HtmlConfig {
     /// If enabled, the sidebar includes navigation for headers on the current
     /// page. Default is `true`.
     pub sidebar_header_nav: bool,
+    /// File extensions to exclude when copying files from the source directory.
+    /// These files will not be copied to the output directory.
+    /// By default, only `.md` files are excluded.
+    /// Example: `["md", "rs", "toml"]`
+    #[serde(rename = "copy-exclude-extensions")]
+    pub copy_exclude_extensions: Vec<String>,
 }
 
 impl Default for HtmlConfig {
@@ -548,6 +554,7 @@ impl Default for HtmlConfig {
             redirect: HashMap::new(),
             hash_files: true,
             sidebar_header_nav: true,
+            copy_exclude_extensions: Vec::new(),
         }
     }
 }

crates/mdbook-html/src/html_handlebars/hbs_renderer.rs

@@ -444,7 +444,12 @@ impl Renderer for HtmlHandlebars {
             .context("Unable to emit redirects")?;
 
         // Copy all remaining files, avoid a recursive copy from/to the book build dir
-        fs::copy_files_except_ext(&src_dir, destination, true, Some(&build_dir), &["md"])?;
+        let exclude_exts: Vec<&str> = html_config
+            .copy_exclude_extensions
+            .iter()
+            .map(|s| s.as_str())
+            .collect();
+        fs::copy_files_except_ext(&src_dir, destination, true, Some(&build_dir), &exclude_exts)?;
 
         info!("HTML book written to `{}`", destination.display());
 

guide/src/cli/build.md

@@ -34,7 +34,24 @@ book. Relative paths are interpreted relative to the current directory. If
 not specified it will default to the value of the `build.build-dir` key in
 `book.toml`, or to `./book`.
 
+#### `--copy-exclude-extensions`
+
+The `--copy-exclude-extensions` option allows you to exclude specific file extensions
+when copying files from the source directory to the build directory. This is useful when
+your source directory contains symlinks to other directories with files you don't want to
+include in the output.
+
+Provide a comma-separated list of extensions (without dots):
+
+```bash
+mdbook build --copy-exclude-extensions rs,toml,lock
+```
+
+This supplements any extensions configured in `book.toml` via the
+`output.html.copy-exclude-extensions` setting.
+
 -------------------
 
-***Note:*** *The build command copies all files (excluding files with `.md` extension) from the source directory
-into the build directory.*
+***Note:*** *The build command copies all files from the source directory into the build directory.
+You can exclude specific file extensions using the `--copy-exclude-extensions` flag or the
+`output.html.copy-exclude-extensions` configuration option.*

guide/src/format/configuration/renderers.md

@@ -111,6 +111,7 @@ site-url = "/example-book/"
 cname = "myproject.rs"
 input-404 = "not-found.md"
 sidebar-header-nav = true
+copy-exclude-extensions = ["rs", "toml"]
 ```
 
 The following configuration options are available:
@@ -170,6 +171,10 @@ The following configuration options are available:
   Static CSS and JS files can reference each other using `{{ resource "filename" }}` directives.
   Defaults to `true`.
 - **sidebar-header-nav:** If `true`, the sidebar will contain navigation for headers on the current page. Default is `true`.
+- **copy-exclude-extensions:** A list of file extensions to exclude when copying files from the source directory
+  to the build directory. By default, all files are copied. This is useful when your source directory contains
+  symlinks to other directories with files you don't want to include in the output. Provide extensions without dots.
+  Example: `["rs", "toml", "lock"]`. Defaults to `[]` (no exclusions).
 
 [custom domain]: https://docs.github.com/en/github/working-with-github-pages/managing-a-custom-domain-for-your-github-pages-site
 

src/cmd/build.rs

@@ -11,6 +11,7 @@ pub fn make_subcommand() -> Command {
         .arg_dest_dir()
         .arg_root_dir()
         .arg_open()
+        .arg_copy_exclude_extensions()
 }
 
 // Build command implementation
@@ -20,6 +21,20 @@ pub fn execute(args: &ArgMatches) -> Result<()> {
 
     set_dest_dir(args, &mut book);
 
+    // Apply CLI copy-exclude-extensions to config
+    if let Some(exts) = args.get_one::<String>("copy-exclude-extensions") {
+        let additional_exts: Vec<String> = exts
+            .split(',')
+            .map(|s| s.trim().to_string())
+            .filter(|s| !s.is_empty())
+            .collect();
+
+        if let Ok(Some(mut html_config)) = book.config.get::<mdbook_core::config::HtmlConfig>("output.html") {
+            html_config.copy_exclude_extensions.extend(additional_exts);
+            book.config.set("output.html", html_config)?;
+        }
+    }
+
     book.build()?;
 
     if args.get_flag("open") {

src/cmd/command_prelude.rs

@@ -38,6 +38,19 @@ pub trait CommandExt: Sized {
         self._arg(arg!(-o --open "Opens the compiled book in a web browser"))
     }
 
+    fn arg_copy_exclude_extensions(self) -> Self {
+        self._arg(
+            Arg::new("copy-exclude-extensions")
+                .long("copy-exclude-extensions")
+                .value_name("EXTENSIONS")
+                .help(
+                    "Comma-separated list of file extensions to exclude when copying files\n\
+                    from the source directory (e.g., 'rs,toml,lock')\n\
+                    This supplements any extensions configured in book.toml.",
+                )
+        )
+    }
+
     #[cfg(any(feature = "watch", feature = "serve"))]
     fn arg_watcher(self) -> Self {
         #[cfg(feature = "watch")]