fix(bls): combine the options of every options line

The Boot Loader Specification allows the options key to appear more
than once, with all of the options combined in order. Each options line
replaced the previous one instead, so an entry that set root= on one
line and other options on the next booted without its root filesystem.

crates/bls/src/lib.rs

@@ -66,9 +66,17 @@ impl FromStr for BlsEntry {
                     title = Some(value.trim().to_string());
                 }
 
-                // The options to pass to the entry.
+                // The options to pass to the entry. The options key can appear more than once,
+                // and all the options are combined in the order they appear.
                 "options" => {
-                    options = Some(value.trim().to_string());
+                    let value = value.trim();
+                    match options.as_mut() {
+                        Some(options) => {
+                            options.push(' ');
+                            options.push_str(value);
+                        }
+                        None => options = Some(value.to_string()),
+                    }
                 }
 
                 // The path to the linux kernel.
@@ -571,6 +579,13 @@ efi        /EFI/fedora/shimx64.efi
         assert_eq!(entry.initrd, ["/intel-ucode.img", "/initramfs.img"]);
     }
 
+    #[test]
+    fn parse_multiple_options_lines_combined_in_order() {
+        let input = "linux /vmlinuz\noptions root=/dev/sda1 ro\noptions quiet\n";
+        let entry: BlsEntry = input.parse().unwrap();
+        assert_eq!(entry.options().as_deref(), Some("root=/dev/sda1 ro quiet"));
+    }
+
     #[test]
     fn initrd_paths_normalises_slashes() {
         let entry: BlsEntry = "linux /vmlinuz\ninitrd /boot/initrd.img\n".parse().unwrap();