Added diff-fenced coder

aider/coders/editblock_fenced_prompts.py

@@ -0,0 +1,95 @@
+# flake8: noqa: E501
+
+from .editblock_prompts import EditBlockPrompts
+
+
+class EditBlockFencedPrompts(EditBlockPrompts):
+    example_messages = [
+        dict(
+            role="user",
+            content="Change get_factorial() to use math.factorial",
+        ),
+        dict(
+            role="assistant",
+            content="""To make this change we need to modify `mathweb/flask/app.py` to:
+
+1. Import the math package.
+2. Remove the existing factorial() function.
+3. Update get_factorial() to call math.factorial instead.
+
+Here are the *SEARCH/REPLACE* blocks:
+
+{fence[0]}
+mathweb/flask/app.py
+<<<<<<< SEARCH
+from flask import Flask
+=======
+import math
+from flask import Flask
+>>>>>>> REPLACE
+{fence[1]}
+
+{fence[0]}
+mathweb/flask/app.py
+<<<<<<< SEARCH
+def factorial(n):
+    "compute factorial"
+
+    if n == 0:
+        return 1
+    else:
+        return n * factorial(n-1)
+
+=======
+>>>>>>> REPLACE
+{fence[1]}
+
+{fence[0]}
+mathweb/flask/app.py
+<<<<<<< SEARCH
+    return str(factorial(n))
+=======
+    return str(math.factorial(n))
+>>>>>>> REPLACE
+{fence[1]}
+<<<<<<< HEAD
+""",
+        ),
+        dict(
+            role="user",
+            content="Refactor hello() into its own file.",
+        ),
+        dict(
+            role="assistant",
+            content="""To make this change we need to modify `main.py` and make a new file `hello.py`:
+
+1. Make a new hello.py file with hello() in it.
+2. Remove hello() from main.py and replace it with an import.
+
+Here are the *SEARCH/REPLACE* blocks:
+
+{fence[0]}
+hello.py
+<<<<<<< SEARCH
+=======
+def hello():
+    "print a greeting"
+
+    print("hello")
+>>>>>>> REPLACE
+{fence[1]}
+
+{fence[0]}
+main.py
+<<<<<<< SEARCH
+def hello():
+    "print a greeting"
+
+    print("hello")
+=======
+from hello import hello
+>>>>>>> REPLACE
+{fence[1]}
+""",
+        ),
+    ]