Update disk image builder to use the builder pattern (Return &mut self)

Author: jasoncouture

src/lib.rs

@@ -45,26 +45,27 @@ impl<'a> DiskImageBuilder<'a> {
         Self { files: Vec::new() }
     }
     /// Add or replace a ramdisk to be included in the final image.
-    pub fn set_ramdisk(&mut self, path: &'a PathBuf) {
-        self.add_or_replace_file(path, RAMDISK_FILE_NAME);
+    pub fn set_ramdisk(&mut self, path: &'a PathBuf) -> &mut Self {
+        self.add_or_replace_file(path, RAMDISK_FILE_NAME)
     }
 
     /// Add or replace a kernel to be included in the final image.
-    pub fn set_kernel(&mut self, path: &'a PathBuf) {
+    pub fn set_kernel(&mut self, path: &'a PathBuf) -> &mut Self {
         self.add_or_replace_file(path, KERNEL_FILE_NAME)
     }
 
     /// Add or replace arbitrary files.
     /// NOTE: You can overwrite internal files if you choose, such as EFI/BOOT/BOOTX64.EFI
     /// This can be useful in situations where you want to generate an image, but not use the provided bootloader.
-    pub fn add_or_replace_file(&mut self, path: &'a PathBuf, target: &'a str) {
+    pub fn add_or_replace_file(&mut self, path: &'a PathBuf, target: &'a str)  -> &mut Self {
         self.files.insert(
             0,
             DiskImageFile::<'a> {
                 source: &path,
                 destination: &target,
             },
         );
+        self
     }
     fn create_fat_filesystem_image(
         &self,