fix(ci): treat an edit to a listed item as maintenance

The validator counted every `+- [` line in the diff as a new submission.
A change to an entry that is already listed produces such a line, so any
correction to an existing item, a typo, a description, a badge, was told
to use the `Add:` title and the new-item template.

Compare the added line against the line it replaced, and report a new
item only when that name and URL were not listed before.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: nibzard

scripts/test_validate_contribution.py

@@ -5,7 +5,12 @@
 
 import unittest
 
-from validate_contribution import REQUIRED_BODY_SECTIONS, extract_body_sections, normalize_section
+from validate_contribution import (
+    REQUIRED_BODY_SECTIONS,
+    extract_body_sections,
+    new_items_in_diff,
+    normalize_section,
+)
 
 
 BODY = """## Summary
@@ -63,5 +68,33 @@ def test_empty_section_is_not_reported(self) -> None:
         self.assertFalse(sections.get("Public reference"))
 
 
+ITEM = "- [Zoom Search](https://github.com/goofrey/zoom-search) - A tool."
+BADGED = ITEM + " ![stars](https://img.shields.io/github/stars/goofrey/zoom-search?style=social)"
+
+
+class NewItemsInDiffTest(unittest.TestCase):
+    def test_added_line_is_a_new_item(self) -> None:
+        diff = "--- a/README.md\n+++ b/README.md\n@@ -1 +1,2 @@\n+" + ITEM
+        self.assertEqual(new_items_in_diff(diff), [ITEM])
+
+    def test_edited_line_is_not_a_new_item(self) -> None:
+        # Changing the text of an entry that is already listed is maintenance.
+        diff = "--- a/README.md\n+++ b/README.md\n@@ -1 +1 @@\n-" + ITEM + "\n+" + BADGED
+        self.assertEqual(new_items_in_diff(diff), [])
+
+    def test_an_edit_does_not_hide_a_new_item(self) -> None:
+        other = "- [Other](https://example.com) - Another tool."
+        diff = ("--- a/README.md\n+++ b/README.md\n@@ -1 +1,2 @@\n"
+                "-" + ITEM + "\n+" + BADGED + "\n+" + other)
+        self.assertEqual(new_items_in_diff(diff), [other])
+
+    def test_removal_alone_adds_nothing(self) -> None:
+        diff = "--- a/README.md\n+++ b/README.md\n@@ -1 +0,0 @@\n-" + ITEM
+        self.assertEqual(new_items_in_diff(diff), [])
+
+    def test_diff_headers_are_ignored(self) -> None:
+        self.assertEqual(new_items_in_diff("--- a/README.md\n+++ b/README.md\n"), [])
+
+
 if __name__ == "__main__":
     unittest.main()

scripts/validate_contribution.py

@@ -60,15 +60,34 @@ def changed_files(base_sha: str) -> set[str]:
     return {line.strip() for line in diff.splitlines() if line.strip()}
 
 
+def item_key(item_line: str) -> tuple[str, str] | None:
+    match = ITEM_LINE_RE.match(item_line)
+    if not match:
+        return None
+    return match.group("name").strip(), match.group("url").strip()
+
+
+def new_items_in_diff(diff: str) -> list[str]:
+    new_lines: list[str] = []
+    changed_keys: set[tuple[str, str]] = set()
+    for line in diff.splitlines():
+        if line.startswith(("+++", "---")):
+            continue
+        if re.match(r"^\+- \[", line):
+            new_lines.append(line[1:])
+        elif re.match(r"^-- \[", line):
+            key = item_key(line[1:])
+            if key:
+                changed_keys.add(key)
+    # A rewritten line for an item that was already listed is an edit, not a submission.
+    return [line for line in new_lines if item_key(line) not in changed_keys]
+
+
 def added_item_lines(base_sha: str) -> list[tuple[str, str]]:
     added: list[tuple[str, str]] = []
     for path in ("README.md", "ARCHIVE.md"):
         diff = run_git("diff", "--unified=0", f"{base_sha}...HEAD", "--", path)
-        for line in diff.splitlines():
-            if line.startswith("+++"):
-                continue
-            if re.match(r"^\+- \[", line):
-                added.append((path, line[1:]))
+        added.extend((path, line) for line in new_items_in_diff(diff))
     return added