Fix generation of edit links

The `IndexPreprocessor` rewrites the path for files
named `README.md` to be `index.md`. This breaks the edit link
in some circumstances.

To address this issues, the `Chapter` struct has now a new attribute
called `source_path`. This is initialized with the same value as
`path`, but is never ever changed.

Finally, the edit link is built by using the `source_path` rather
than the `path`.

src/book/book.rs

@@ -160,6 +160,8 @@ pub struct Chapter {
     pub sub_items: Vec<BookItem>,
     /// The chapter's location, relative to the `SUMMARY.md` file.
     pub path: Option<PathBuf>,
+    /// The chapter's source file, relative to the `SUMMARY.md` file.
+    pub source_path: Option<PathBuf>,
     /// An ordered list of the names of each chapter above this one in the hierarchy.
     pub parent_names: Vec<String>,
 }
@@ -169,13 +171,15 @@ impl Chapter {
     pub fn new<P: Into<PathBuf>>(
         name: &str,
         content: String,
-        path: P,
+        p: P,
         parent_names: Vec<String>,
     ) -> Chapter {
+        let path: PathBuf = p.into();
         Chapter {
             name: name.to_string(),
             content,
-            path: Some(path.into()),
+            path: Some(path.clone()),
+            source_path: Some(path),
             parent_names,
             ..Default::default()
         }
@@ -188,6 +192,7 @@ impl Chapter {
             name: name.to_string(),
             content: String::new(),
             path: None,
+            source_path: None,
             parent_names,
             ..Default::default()
         }
@@ -438,6 +443,7 @@ And here is some \
             content: String::from("Hello World!"),
             number: Some(SectionNumber(vec![1, 2])),
             path: Some(PathBuf::from("second.md")),
+            source_path: Some(PathBuf::from("second.md")),
             parent_names: vec![String::from("Chapter 1")],
             sub_items: Vec::new(),
         };
@@ -446,6 +452,7 @@ And here is some \
             content: String::from(DUMMY_SRC),
             number: None,
             path: Some(PathBuf::from("chapter_1.md")),
+            source_path: Some(PathBuf::from("chapter_1.md")),
             parent_names: Vec::new(),
             sub_items: vec![
                 BookItem::Chapter(nested.clone()),
@@ -470,6 +477,7 @@ And here is some \
                 name: String::from("Chapter 1"),
                 content: String::from(DUMMY_SRC),
                 path: Some(PathBuf::from("chapter_1.md")),
+                source_path: Some(PathBuf::from("chapter_1.md")),
                 ..Default::default()
             })],
             ..Default::default()
@@ -510,6 +518,7 @@ And here is some \
                     content: String::from(DUMMY_SRC),
                     number: None,
                     path: Some(PathBuf::from("Chapter_1/index.md")),
+                    source_path: Some(PathBuf::from("Chapter_1/index.md")),
                     parent_names: Vec::new(),
                     sub_items: vec![
                         BookItem::Chapter(Chapter::new(
@@ -562,6 +571,7 @@ And here is some \
                     content: String::from(DUMMY_SRC),
                     number: None,
                     path: Some(PathBuf::from("Chapter_1/index.md")),
+                    source_path: Some(PathBuf::from("Chapter_1/index.md")),
                     parent_names: Vec::new(),
                     sub_items: vec![
                         BookItem::Chapter(Chapter::new(

src/config.rs

@@ -559,6 +559,7 @@ impl Default for HtmlConfig {
             search: None,
             git_repository_url: None,
             git_repository_icon: None,
+            git_repository_edit_url_template: None,
             input_404: None,
             site_url: None,
             cname: None,

src/renderer/html_handlebars/hbs_renderer.rs

@@ -40,7 +40,12 @@ impl HtmlHandlebars {
         if let Some(ref git_repository_edit_url_template) =
             ctx.html_config.git_repository_edit_url_template
         {
-            let full_path = "src/".to_owned() + path.to_str().unwrap();
+            let full_path = "src/".to_owned()
+                + ch.source_path
+                    .clone()
+                    .unwrap_or_default()
+                    .to_str()
+                    .unwrap_or_default();
             let edit_url = git_repository_edit_url_template.replace("{path}", &full_path);
             ctx.data
                 .insert("git_repository_edit_url".to_owned(), json!(edit_url));