aider: Implemented replace_part_with_missing_leading_whitespace function to find and replace the portion of whole that matches part with the same leading whitespace and replace it with replace containing the same leading whitespace.

# Context:
USER: in `replace_part_with_missing_leading_whitespace`, we want to find the string part in whole and replace it with the string `replace`. but `part` may not exactly occur in whole. instead, every line of part appears in whole with a fixed amount of extra whitespace in front of it. so every line in part might appear in whole with 4 spaces prepended. or every line might have 2 tabs. always the exact same whitespaces. finish implementing this function so that it finds the portion of whole which matches part in this manner (if any) and replace it with `replace` where replace is updated to contain that repeated/omitted whitespace.
ASSISTANT: To implement the `replace_part_with_missing_leading_whitespace` function, follow these steps:

1. Split `whole` and `part` into lines.
2. Iterate through the lines of `whole` and find the first line that matches the first line of `part` with any leading whitespace.
3. Check if the following lines in `whole` also match the remaining lines in `part` with the same leading whitespace.
4. If all lines match, replace the matched lines in `whole` with the lines in `replace` with the same leading whitespace.
5. Return the modified `whole` or `None` if no match is found.

Here's the updated function:

```python
aider/utils.py
<<<<<<< ORIGINAL
def replace_part_with_missing_leading_whitespace(whole, part, replace):
    pass
=======
def replace_part_with_missing_leading_whitespace(whole, part, replace):
    whole_lines = whole.splitlines()
    part_lines = part.splitlines()
    replace_lines = replace.splitlines()

    for i in range(len(whole_lines) - len(part_lines) + 1):
        leading_whitespace = ""
        for j, c in enumerate(whole_lines[i]):
            if c == part_lines[0][0]:
                leading_whitespace = whole_lines[i][:j]
                break

        if not leading_whitespace:
            continue

        matched = all(
            whole_lines[i + k].startswith(leading_whitespace + part_lines[k])
            for k in range(len(part_lines))
        )

        if matched:
            for k in range(len(part_lines)):
                whole_lines[i + k] = leading_whitespace + replace_lines[k]
            return "\n".join(whole_lines)

    return None
>>>>>>> UPDATED
```

This implementation should find the portion of `whole` that matches `part` with the same leading whitespace and replace it with `replace` containing the same leading whitespace.

aider/utils.py

@@ -60,7 +60,31 @@ def try_dotdotdots(whole, part, replace):
 
 
 def replace_part_with_missing_leading_whitespace(whole, part, replace):
-    pass
+    whole_lines = whole.splitlines()
+    part_lines = part.splitlines()
+    replace_lines = replace.splitlines()
+
+    for i in range(len(whole_lines) - len(part_lines) + 1):
+        leading_whitespace = ""
+        for j, c in enumerate(whole_lines[i]):
+            if c == part_lines[0][0]:
+                leading_whitespace = whole_lines[i][:j]
+                break
+
+        if not leading_whitespace:
+            continue
+
+        matched = all(
+            whole_lines[i + k].startswith(leading_whitespace + part_lines[k])
+            for k in range(len(part_lines))
+        )
+
+        if matched:
+            for k in range(len(part_lines)):
+                whole_lines[i + k] = leading_whitespace + replace_lines[k]
+            return "\n".join(whole_lines)
+
+    return None
 
 
 def replace_most_similar_chunk(whole, part, replace):