idiff acceptance fix (SciTools#5482)

* removed duplication case in Accept

* updated docstring

* corrected whatsnew (hopefully)

* the merge undid the fix. Here we go

* removed trailng . from whatsnew

* changed ref to mod

Author: ESadek-MO

docs/src/whatsnew/latest.rst

@@ -38,6 +38,9 @@ This document explains the changes made to Iris for this release
 
 #. `@scottrobinson02`_ fixed the output units when dividing a coordinate by a
    cube. (:issue:`5305`, :pull:`5331`)
+   
+#. `@ESadek-MO`_ has updated :mod:`iris.tests.graphics.idiff` to stop duplicated file names
+   preventing acceptance. (:issue:`5098`, :pull:`5482`)
 
 
 💣 Incompatible Changes

lib/iris/tests/graphics/idiff.py

@@ -73,17 +73,12 @@ def diff_viewer(
     repo = graphics.read_repo_json()
 
     def accept(event):
-        if test_id not in repo:
-            repo[test_id] = phash
-            graphics.write_repo_json(repo)
-            out_file = result_dir / (test_id + ".png")
-            result_path.rename(out_file)
-            msg = f"ACCEPTED:  {result_path.name} -> {out_file.name}"
-            print(msg)
-        else:
-            msg = f"DUPLICATE: {result_path.name} -> {expected_path.name} (ignored)"
-            print(msg)
-            result_path.unlink()
+        repo[test_id] = phash
+        graphics.write_repo_json(repo)
+        out_file = result_dir / (test_id + ".png")
+        result_path.rename(out_file)
+        msg = f"ACCEPTED:  {result_path.name} -> {out_file.name}"
+        print(msg)
         diff_fname.unlink()
         plt.close()