Improve PathBuf usage

src/cmd/shelf.rs

@@ -59,17 +59,20 @@ pub fn execute(_args: &ArgMatches) -> Result<()> {
 
     let _ = std::fs::remove_dir_all("shelf");
     let _ = std::fs::remove_dir_all("repositories");
-    let _ = MDBook::init("shelf").create_gitignore(false).build();
+    let shelf_book = MDBook::init("shelf").create_gitignore(false).build()?;
 
-    let index_file_name = "shelf/src/index.md";
+    let mut index_file_name = shelf_book.source_dir();
+    index_file_name.push("index.md");
     let mut index_file = File::create(index_file_name).unwrap();
-    let mut summary = File::create("shelf/src/SUMMARY.md").unwrap();
-    writeln!(summary, "# Summary")?;
-    writeln!(summary, "- [Index](./index.md)")?;
-
     writeln!(index_file, "# Bookshelf")?;
     writeln!(index_file)?;
 
+    let mut summary_file_name = shelf_book.source_dir();
+    summary_file_name.push("SUMMARY.md");
+    let mut summary = File::create(summary_file_name).unwrap();
+    writeln!(summary, "# Summary")?;
+    writeln!(summary, "- [Index](./index.md)")?;
+
     for sb in &shelf.book {
         if let Some(url) = &sb.git_url {
             println!("{:?}", sb);