Fix steps_to_run for shared config files

With this merge, each task that uses a shared config file used
by a task to be set up has its configure() method called and
then `steps_to_run` is added to the shared config options.  This
prevents a situation where `steps_to_run` is missing when a
task is set up later that overwrites the shared config file.

polaris/config.py

@@ -25,6 +25,8 @@ class PolarisConfigParser(MpasConfigParser):
         A list of filepaths within the component's work directory where
         symlinks to ``filepath`` will be created
 
+    symlinks : set of polaris.Task
+        A list of tasks that use this config
     """
 
     def __init__(self, filepath=None):
@@ -40,6 +42,7 @@ def __init__(self, filepath=None):
         super().__init__()
         self.filepath: Union[str, None] = filepath
         self.symlinks = list()
+        self.tasks = set()
 
     def setup(self):
         """

polaris/setup.py

@@ -370,13 +370,14 @@ def _configure_tasks_and_add_step_configs(tasks, component, initial_configs,
     Call the configure() method for each task and add configs to "owned" steps
     """
 
-    for task in tasks.values():
-        task.configure()
-        task.config.set(section=f'{task.name}',
-                        option='steps_to_run',
-                        value=' '.join(task.steps_to_run),
-                        comment=f'A list of steps to include when running the '
-                                f'{task.name} task')
+    for config in initial_configs.values():
+        for task in config.tasks:
+            task.configure()
+            task.config.set(section=f'{task.name}',
+                            option='steps_to_run',
+                            value=' '.join(task.steps_to_run),
+                            comment=f'A list of steps to include when running '
+                                    f'the {task.name} task')
 
     # add configs to steps after calling task.configure() on all tasks in case
     # new steps were added

polaris/task.py

@@ -100,6 +100,7 @@ def __init__(self, component, name, subdir=None, indir=None):
         self.path = os.path.join(self.component.name, self.subdir)
         self.config = PolarisConfigParser()
         self.config_filename = ''
+        self.config.tasks.add(self)
 
         # steps will be added by calling add_step()
         self.steps = dict()
@@ -219,6 +220,7 @@ def set_shared_config(self, config, link=None):
         self.component.add_config(config)
 
         self.config = config
+        config.tasks.add(self)
         if link is None:
             directory, basename = os.path.split(config.filepath)
             if directory != self.subdir: