Honor Registrator branch when creating releases

tagbot/action/repo.py

@@ -329,9 +329,23 @@ def _registry_url(self) -> Optional[str]:
             raise InvalidProject("Package.toml is missing the 'repo' key")
         return self.__registry_url
 
-    @property
-    def _release_branch(self) -> str:
-        """Get the name of the release branch."""
+    def _release_branch(self, version: str) -> str:
+        """Get the name of the release branch for a specific version.
+
+        Priority:
+        1. Branch specified by Registrator invocation (from PR body)
+        2. Release branch specified in TagBot config
+        3. Default branch
+        """
+        # First check if Registrator specified a branch for this version
+        try:
+            pr_branch = self._branch_from_registry_pr(version)
+        except Exception as e:
+            logger.debug(f"Skipping registry PR branch lookup: {e}")
+            pr_branch = None
+        if pr_branch:
+            return pr_branch
+        # Fall back to config branch or default
         return self.__release_branch or self._repo.default_branch
 
     def _only(self, val: Union[T, List[T]]) -> T:
@@ -498,6 +512,25 @@ def _registry_pr(self, version: str) -> Optional[PullRequest]:
         logger.debug(f"Did not find registry PR for branch {head}")
         return None
 
+    def _branch_from_registry_pr(self, version: str) -> Optional[str]:
+        """Extract release branch name from registry PR body.
+
+        Registrator includes branch info in PR body like:
+        - Branch: my-branch
+        """
+        pr = self._registry_pr(version)
+        if not pr:
+            return None
+        if not pr.body:
+            return None
+        # Look for "- Branch: <branch_name>" or "Branch: <branch_name>" in PR body
+        m = re.search(r"^-?\s*Branch:\s*(.+)$", pr.body, re.MULTILINE)
+        if m:
+            branch = m[1].strip()
+            logger.debug(f"Found branch '{branch}' in registry PR for {version}")
+            return branch
+        return None
+
     def _commit_sha_from_registry_pr(self, version: str, tree: str) -> Optional[str]:
         """Look up the commit SHA of version from its registry PR."""
         pr = self._registry_pr(version)
@@ -669,9 +702,9 @@ def _commit_sha_of_tag(self, version_tag: str) -> Optional[str]:
             return resolved_sha
         return sha
 
-    def _commit_sha_of_release_branch(self) -> str:
-        """Get the latest commit SHA of the release branch."""
-        branch = self._repo.get_branch(self._release_branch)
+    def _commit_sha_of_release_branch(self, version: str) -> str:
+        """Get the latest commit SHA of the release branch for a specific version."""
+        branch = self._repo.get_branch(self._release_branch(version))
         return cast(str, branch.commit.sha)
 
     def _highest_existing_version(self) -> Optional[VersionInfo]:
@@ -1429,10 +1462,10 @@ def create_release(self, version: str, sha: str, is_latest: bool = True) -> None
                        them as latest.
         """
         target = sha
-        if self._commit_sha_of_release_branch() == sha:
+        if self._commit_sha_of_release_branch(version) == sha:
             # If we use <branch> as the target, GitHub will show
             # "<n> commits to <branch> since this release" on the release page.
-            target = self._release_branch
+            target = self._release_branch(version)
         version_tag = self._get_version_tag(version)
         logger.debug(f"Release {version_tag} target: {target}")
         # Check if a release for this tag already exists before doing work

test/action/test_repo.py

@@ -281,9 +281,25 @@ def test_registry_url_missing_repo_key():
 def test_release_branch():
     r = _repo()
     r._repo = Mock(default_branch="a")
-    assert r._release_branch == "a"
+    r._registry_pr = Mock(return_value=None)
+    assert r._release_branch("v1.0.0") == "a"
+
     r = _repo(branch="b")
-    assert r._release_branch == "b"
+    r._registry_pr = Mock(return_value=None)
+    assert r._release_branch("v1.0.0") == "b"
+
+    # Test PR branch has highest priority
+    r = _repo(branch="config-branch")
+    r._repo = Mock(default_branch="default-branch")
+    pr_body = "foo\n- Branch: pr-branch\nbar"
+    r._registry_pr = Mock(return_value=Mock(body=pr_body))
+    assert r._release_branch("v1.0.0") == "pr-branch"
+
+    # Test that missing branch in PR falls back to config
+    r = _repo(branch="config-branch")
+    r._repo = Mock(default_branch="default-branch")
+    r._registry_pr = Mock(return_value=Mock(body="no branch here"))
+    assert r._release_branch("v1.0.0") == "config-branch"
 
 
 def test_only():
@@ -477,6 +493,39 @@ def test_commit_sha_from_registry_pr(logger):
     assert r._commit_sha_from_registry_pr("v4.5.6", "def") == "sha"
 
 
+@patch("tagbot.action.repo.logger")
+def test_branch_from_registry_pr(logger):
+    """Test extracting branch from registry PR body."""
+    r = _repo()
+
+    # No PR found
+    r._registry_pr = Mock(return_value=None)
+    assert r._branch_from_registry_pr("v1.0.0") is None
+
+    # PR body without branch info
+    r._registry_pr.return_value = Mock(body="foo\nbar\nbaz")
+    assert r._branch_from_registry_pr("v1.0.0") is None
+
+    # PR body is None
+    r._registry_pr.return_value.body = None
+    assert r._branch_from_registry_pr("v1.0.0") is None
+
+    # PR body with "- Branch: <branch_name>" format
+    r._registry_pr.return_value.body = "foo\n- Branch: my-release-branch\nbar"
+    assert r._branch_from_registry_pr("v1.0.0") == "my-release-branch"
+    logger.debug.assert_called_with(
+        "Found branch 'my-release-branch' in registry PR for v1.0.0"
+    )
+
+    # PR body with "Branch: <branch_name>" format (without dash)
+    r._registry_pr.return_value.body = "foo\nBranch: another-branch\nbar"
+    assert r._branch_from_registry_pr("v2.0.0") == "another-branch"
+
+    # PR body with extra whitespace
+    r._registry_pr.return_value.body = "foo\n-   Branch:   spaced-branch  \nbar"
+    assert r._branch_from_registry_pr("v3.0.0") == "spaced-branch"
+
+
 def test_commit_sha_of_tree():
     """Test tree→commit lookup using git log cache."""
     r = _repo()
@@ -673,8 +722,9 @@ def test_version_with_latest_commit_marks_latest_when_newer(logger):
 def test_commit_sha_of_release_branch():
     r = _repo()
     r._repo = Mock(default_branch="a")
+    r._registry_pr = Mock(return_value=None)
     r._repo.get_branch.return_value.commit.sha = "sha"
-    assert r._commit_sha_of_release_branch() == "sha"
+    assert r._commit_sha_of_release_branch("v1.0.0") == "sha"
     r._repo.get_branch.assert_called_with("a")
 
 
@@ -1020,6 +1070,7 @@ def test_handle_release_branch_subdir():
 def test_create_release():
     r = _repo(user="user", email="email")
     r._commit_sha_of_release_branch = Mock(return_value="a")
+    r._registry_pr = Mock(return_value=None)
     r._git.create_tag = Mock()
     r._repo = Mock(default_branch="default")
     r._repo.create_git_tag.return_value.sha = "t"
@@ -1118,6 +1169,7 @@ def test_create_release_handles_existing_release_error():
 def test_create_release_subdir():
     r = _repo(user="user", email="email", subdir="path/to/Foo.jl")
     r._commit_sha_of_release_branch = Mock(return_value="a")
+    r._registry_pr = Mock(return_value=None)
     r._repo.get_contents = Mock(
         return_value=Mock(decoded_content=b"""name = "Foo"\nuuid="abc-def"\n""")
     )