little bugfix in commit checker

Author: hjwp

tests/sourcetree.py

@@ -263,6 +263,10 @@ def check_chunks_against_future_contents(listing_contents, future_contents):
                     f"{len(missing_lines)} lines did not match future contents"
                 )
             else:
+                print('reindented listing')
+                print(repr(reindented_chunk))
+                print('future contents')
+                print(repr(future_contents))
                 raise ApplyCommitException(f"Commit lines in wrong order (?)")
 
 
@@ -301,7 +305,10 @@ def split_into_chunks(code):
             yield chunk
             chunk = ""
         else:
-            chunk = f"{chunk}\n{line}"
+            if chunk:
+                chunk = f"{chunk}\n{line}"
+            else:
+                chunk = line
 
     if chunk:
         yield chunk

tests/test_sourcetree.py

@@ -825,6 +825,25 @@ def method1(self):
             check_chunks_against_future_contents(code, future_contents)
 
 
+    def test_leading_blank_lines_in_listing_are_ignored(self):
+        code = dedent(
+            """
+            def method1(self):
+                # amend method 1
+                return 2
+
+            """
+        )
+        future_contents = dedent(
+            """
+            class Thing:
+                def method1(self):
+                    # amend method 1
+                    return 2
+            """
+        ).strip()
+        check_chunks_against_future_contents(code, future_contents)  # should not raise
+
     def test_trailing_blank_lines_in_listing_are_ignored(self):
         code = dedent(
             """