nixos/limine: tidy up the boot menu

nixos/modules/system/boot/loader/limine/limine-install.py

@@ -168,14 +168,29 @@ def config_entry(levels: int, bootspec: BootSpec, label: str, time: str) -> str:
     return entry
 
 
-def generate_config_entry(profile: str, gen: str) -> str:
+def generate_config_entry(profile: str, gen: str, special: bool) -> str:
     time = datetime.datetime.fromtimestamp(os.stat(get_system_path(profile,gen), follow_symlinks=False).st_mtime).strftime("%F %H:%M:%S")
     boot_json = json.load(open(os.path.join(get_system_path(profile, gen), 'boot.json'), 'r'))
     boot_spec = bootjson_to_bootspec(boot_json)
 
-    entry = config_entry(2, boot_spec, f'Generation {gen}', time)
-    for spec, spec_boot_spec in boot_spec.specialisations.items():
-        entry += config_entry(2, spec_boot_spec, f'Generation {gen}, Specialisation {spec}', str(time))
+    specialisation_list = boot_spec.specialisations.items()
+    depth = 2
+    entry = ""
+
+    if len(specialisation_list) > 0:
+        depth += 1
+        entry += '/' * (depth-1)
+
+        if special:
+            entry += '+'
+
+        entry += f'Generation {gen}' + '\n'
+        entry += config_entry(depth, boot_spec, f'Default', str(time))
+    else:
+        entry += config_entry(depth, boot_spec, f'Generation {gen}', str(time))
+
+    for spec, spec_boot_spec in specialisation_list:
+        entry += config_entry(depth, spec_boot_spec, f'{spec}', str(time))
     return entry
 
 
@@ -269,13 +284,17 @@ def main():
     editor_enabled = 'yes' if config('enableEditor') else 'no'
     hash_mismatch_panic = 'yes' if config('panicOnChecksumMismatch') else 'no'
 
+    last_gen = get_gens()[-1]
+    last_gen_json = json.load(open(os.path.join(get_system_path('system', last_gen), 'boot.json'), 'r'))
+    last_gen_boot_spec = bootjson_to_bootspec(last_gen_json)
+
     config_file = config('extraConfig') + '\n'
     config_file += textwrap.dedent(f'''
         timeout: {timeout}
         editor_enabled: {editor_enabled}
         hash_mismatch_panic: {hash_mismatch_panic}
         graphics: yes
-        default_entry: 2
+        default_entry: {3 if len(last_gen_boot_spec.specialisations.items()) > 0 else 2}
     ''')
 
     for wallpaper in config('style', 'wallpapers'):
@@ -307,8 +326,11 @@ def main():
         group_name = 'default profile' if profile == 'system' else f"profile '{profile}'"
         config_file += f'/+NixOS {group_name}\n'
 
+        isFirst = True
+
         for gen in sorted(gens, key=lambda x: x, reverse=True):
-            config_file += generate_config_entry(profile, gen)
+            config_file += generate_config_entry(profile, gen, isFirst)
+            isFirst = False
 
     config_file_path = os.path.join(limine_dir, 'limine.conf')
     config_file += '\n# NixOS boot entries end here\n\n'