Remove the book.multilingual field

As it is seems it has never been in real use.

See rust-lang#2636

Author: szabgab

examples/nop-preprocessor.rs

@@ -117,7 +117,6 @@ mod nop_lib {
                         "book": {
                             "authors": ["AUTHOR"],
                             "language": "en",
-                            "multilingual": false,
                             "src": "src",
                             "title": "TITLE"
                         },

src/config.rs

@@ -420,8 +420,6 @@ pub struct BookConfig {
     pub description: Option<String>,
     /// Location of the book source relative to the book's root directory.
     pub src: PathBuf,
-    /// Does this book support more than one language?
-    pub multilingual: bool,
     /// The main language of the book.
     pub language: Option<String>,
     /// The direction of text in the book: Left-to-right (LTR) or Right-to-left (RTL).
@@ -436,7 +434,6 @@ impl Default for BookConfig {
             authors: Vec::new(),
             description: None,
             src: PathBuf::from("src"),
-            multilingual: false,
             language: Some(String::from("en")),
             text_direction: None,
         }
@@ -820,7 +817,6 @@ mod tests {
         title = "Some Book"
         authors = ["Michael-F-Bryan <[email protected]>"]
         description = "A completely useless book"
-        multilingual = true
         src = "source"
         language = "ja"
 
@@ -859,7 +855,6 @@ mod tests {
             title: Some(String::from("Some Book")),
             authors: vec![String::from("Michael-F-Bryan <[email protected]>")],
             description: Some(String::from("A completely useless book")),
-            multilingual: true,
             src: PathBuf::from("source"),
             language: Some(String::from("ja")),
             text_direction: None,

tests/init.rs

@@ -29,7 +29,7 @@ fn base_mdbook_init_should_create_default_content() {
     let contents = fs::read_to_string(temp.path().join("book.toml")).unwrap();
     assert_eq!(
         contents,
-        "[book]\nauthors = []\nlanguage = \"en\"\nmultilingual = false\nsrc = \"src\"\n"
+        "[book]\nauthors = []\nlanguage = \"en\"\nsrc = \"src\"\n"
     );
 }
 
@@ -94,7 +94,7 @@ fn run_mdbook_init_with_custom_book_and_src_locations() {
     let contents = fs::read_to_string(temp.path().join("book.toml")).unwrap();
     assert_eq!(
         contents,
-        "[book]\nauthors = []\nlanguage = \"en\"\nmultilingual = false\nsrc = \"in\"\n\n[build]\nbuild-dir = \"out\"\ncreate-missing = true\nextra-watch-dirs = []\nuse-default-preprocessors = true\n"
+        "[book]\nauthors = []\nlanguage = \"en\"\nsrc = \"in\"\n\n[build]\nbuild-dir = \"out\"\ncreate-missing = true\nextra-watch-dirs = []\nuse-default-preprocessors = true\n"
     );
 }