Allow gh-issue 0 for "no changes" release entries

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## 2.2.0
+
+* Allow `gh-issue 0` for "no changes" release entries by @hugovk in https://github.com/python/blurb/pull/92
+
 ## 2.1.0
 
 * Add support for Python 3.15 by @hugovk in https://github.com/python/blurb/pull/74

src/blurb/_blurb_file.py

@@ -151,7 +151,11 @@ def finish_entry() -> None:
                     except (TypeError, ValueError):
                         throw(f'Invalid {issue_keys[key]} number: {value!r}')
 
-                if key == 'gh-issue' and int(value) < lowest_possible_gh_issue_number:
+                if (
+                    key == 'gh-issue'
+                    and not no_changes
+                    and int(value) < lowest_possible_gh_issue_number
+                ):
                     throw(
                         f'Invalid gh-issue number: {value!r} (must be >= {lowest_possible_gh_issue_number})'
                     )

tests/test_blurb_file.py

@@ -97,6 +97,26 @@ def test_parse():
     assert body == 'Hello world!\n'
 
 
+def test_parse_no_changes():
+    # Arrange
+    contents = (
+        '.. gh-issue: 0\n'
+        '.. no changes: True\n'
+        '.. section: Library\n'
+        'There were no new changes in version 3.15.0.'
+    )
+    blurbs = Blurbs()
+
+    # Act
+    blurbs.parse(contents)
+
+    # Assert
+    metadata, body = blurbs[0]
+    assert metadata['gh-issue'] == '0'
+    assert metadata['no changes'] == 'True'
+    assert body == 'There were no new changes in version 3.15.0.\n'
+
+
 @pytest.mark.parametrize(
     'contents, expected_error',
     (