Add test case: update.file.replace.whole

Author: elifarley

tests/corpus/update.file.replace.whole/1.py

@@ -0,0 +1,2 @@
+class A:
+    pass

tests/corpus/update.file.replace.whole/chat.xml

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+<no-train>
+```CEDARScript
+UPDATE FILE "1.py"
+REPLACE WHOLE
+WITH CONTENT '''
+@0:class B:
+@1:...
+'''
+```
+</no-train>

tests/corpus/update.file.replace.whole/expected.1.py

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+class B:
+    ...