Add documentation and unit tests for `.mdbookignore`

guide/src/format/configuration/renderers.md

@@ -298,6 +298,16 @@ The value can be any valid URI the browser should navigate to (e.g. `https://rus
 This will generate an HTML page which will automatically redirect to the given location.
 Note that the source location does not support `#` anchor redirects.
 
+### `[.mdbookignore]`
+
+You can use a `.mdbookignore` file to exclude files from the build process. The file is places in the `src` directory of your book and has the format known from [`.gitignore`](https://git-scm.com/docs/gitignore) files.
+
+For example:
+```
+*.rs
+/target/
+```
+
 ## Markdown Renderer
 
 The Markdown renderer will run preprocessors and then output the resulting

src/book/mod.rs

@@ -610,7 +610,8 @@ fn preprocessor_should_run(
 mod tests {
     use super::*;
     use std::str::FromStr;
-    use toml::value::Table;
+    use tempfile::Builder as TempFileBuilder;
+    use toml::value::{Table, Value};
 
     #[test]
     fn config_defaults_to_html_renderer_if_empty() {
@@ -879,4 +880,21 @@ mod tests {
         let got = preprocessor_should_run(&BoolPreprocessor(should_be), &html, &cfg);
         assert_eq!(got, should_be);
     }
+
+    #[test]
+    fn build_test_book() {
+        let temp_dir = TempFileBuilder::new().prefix("mdbook-").tempdir().unwrap();
+        let test_book_dir = PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("test_book");
+
+        utils::fs::copy_files_except_ext(&test_book_dir, temp_dir.path(), true, None, None)
+            .expect("Error while copying test book to temp dir");
+
+        let book = MDBook::load(temp_dir.path()).expect("Unable to load book");
+        book.build().expect("Error while building book");
+
+        let book_dir = temp_dir.path().join("book");
+        assert!(book_dir.join("index.html").exists());
+        assert!(book_dir.join(".mdbookignore").exists());
+        assert!(!book_dir.join("ignored_file").exists());
+    }
 }

test_book/src/.mdbookignore

@@ -0,0 +1 @@
+ignored_file

test_book/src/ignored_file

@@ -0,0 +1 @@
+This will not be copied to the book directory.