gh-133722: Add Difflib theme to _colorize and 'color' option to difflib.unified_diff

[dougthor42]

Add a color arg (defaulting to False) to difflib.unified_diff. When True, ANSI color codes are injected to the diff lines so that the printed result looks like git diff --color:

>>> import difflib
>>> args = [['one', 'three'], ['two', 'three'], 'Original', 'Current']
>>> for line in difflib.unified_diff(*args, lineterm='', color=True):
...     print(line)
...     
--- Original
+++ Current
@@ -1,2 +1,2 @@
-one
+two
 three

Fixes #133722.

It's a bummer, I just missed the feature freeze window for 3.14 (it was yesterday! 😭), but c'est la vie!

• Issue: Add a color: bool arg to difflib.unified_diff #133722

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📚 Documentation preview 📚: https://cpython-previews--133725.org.readthedocs.build/