Reapply "Inline split_list and be more idiomatic"

Fix bug with len(list)>1

This reverts commit eec4ce492d58c875a40929e8f299f8215cd96886.

omegastar.py

···
 import logging
 
 
-# Return two halves of the given list. For odd-length lists, the second half
-# will be larger.
-def split_list(items):
-    half = len(items) // 2
-    return items[0:half], items[half:]
-
-
 # Attempt to reduce the `items` argument as much as possible, returning the
 # shorter version. `fixed` will always be used as part of the items when
 # running `command`.
···
     while len(items) > 1:
         logging.info(f"{indent}{len(fixed) + len(items)} candidates")
 
-        left, right = split_list(items)
+        # Return two halves of the given list. For odd-length lists, the second
+        # half will be larger.
+        half = len(items) // 2
+        left = items[0:half]
+        right = items[half:]
         if not command(fixed + left):
             items = left
             continue