diff --git a/aider/diffs.py b/aider/diffs.py
index 621d60c4c..9a0bae9a7 100644
--- a/aider/diffs.py
+++ b/aider/diffs.py
@@ -1,23 +1,48 @@
-import sys
 import difflib
+import sys
+
+from .dump import dump
+
 
 def main():
     if len(sys.argv) != 3:
-        print("Usage: python diffs.py file1 file2")
+        print("Usage: python diffs.py file1 file")
         sys.exit(1)
 
-    file1, file2 = sys.argv[1], sys.argv[2]
+    file_orig, file_updated = sys.argv[1], sys.argv[2]
 
-    with open(file1, 'r') as f1:
-        content1 = f1.readlines()
+    with open(file_orig, "r") as f:
+        lines_orig = f.readlines()
 
-    with open(file2, 'r') as f2:
-        content2 = f2.readlines()
+    with open(file_updated, "r") as f:
+        lines_updated = f.readlines()
 
-    differences = list(difflib.unified_diff(content1, content2, fromfile=file1, tofile=file2))
+    diff = list(difflib.ndiff(lines_orig, lines_updated))
+
+    # Mapping between the line numbers
+    mapping = {}
+
+    num_orig, num_updated = 0, 0
+    last_non_deleted_orig = 0
+
+    for line in diff:
+        print(f"{num_orig:2d} {num_updated:2d} {line}", end="")
+        code = line[0]
+        if code == " ":
+            # lines are the same in both files
+            mapping[num_orig] = num_updated
+            num_orig += 1
+            num_updated += 1
+            last_non_deleted_orig = num_orig
+        elif code == "-":
+            # line only in file_orig
+            num_orig += 1
+        elif code == "+":
+            # line only in file_updated
+            num_updated += 1
+
+    dump(last_non_deleted_orig)
 
-    for line in differences:
-        sys.stdout.write(line)
 
 if __name__ == "__main__":
     main()