Stop Sud.load() from overwriting the configured sud.json on disk

load() used to immediately persist whatever was loaded back to
self.path - the file the server was originally configured with. This
meant any Load (including "New Sud"'s empty schedule) silently
clobbered the currently-configured brew file, with no way to get it
back. load()/save() now operate purely on an in-memory copy; a client
that wants to persist a schedule does so explicitly itself (the GUI's
Save already prompts for a destination - this just removes the
hidden, automatic disk write load() was doing underneath it).

components/sud.py

@@ -52,6 +52,7 @@ class Sud(AttributeChange):
 		self.path = path
 		with open(path) as f:
 			data = json.load(f)
+		self._data = data
 
 		(self.name, self.description, self.schedule,
 			self.pot_mass, self.pot_material) = self._parse_data(data)
@@ -87,16 +88,21 @@ class Sud(AttributeChange):
 		self._paused_from = None
 
 	def save(self):
-		"""Returns the sud.json document currently on disk, for a client to
-		edit and hand back to load()."""
-		with open(self.path) as f:
-			return json.load(f)
+		"""Returns the currently running sud.json document, for a client to
+		edit and hand back to load(). Purely in-memory - load() no longer
+		touches disk, so this is just whatever was last loaded (the file
+		given to __init__, or a later load()), not necessarily what's on
+		disk at self.path anymore."""
+		return self._data
 
 	def load(self, data):
-		"""Replaces the schedule with a new sud.json document and persists
-		it to disk, resetting to IDLE as if freshly loaded from that file.
-		Refused while a brew is in progress, or if data is malformed - in
-		either case the current schedule is left untouched."""
+		"""Replaces the running schedule with a new sud.json document (kept
+		in memory only - never written to disk, so the file originally
+		configured via self.path is never touched by this), resetting to
+		IDLE as if freshly loaded. A client wanting to persist a schedule
+		does so explicitly itself, e.g. by writing save()'s result wherever
+		it chooses. Refused while a brew is in progress, or if data is
+		malformed - in either case the current schedule is left untouched."""
 		if self.state not in (SudState.IDLE, SudState.DONE):
 			return False
 		try:
@@ -105,8 +111,7 @@ class Sud(AttributeChange):
 			return False
 
 		self.name, self.description, self.schedule, self.pot_mass, self.pot_material = parsed
-		with open(self.path, 'w') as f:
-			json.dump(data, f, indent='\t')
+		self._data = data
 
 		self._reset_run_state()
 		return True