Handle new GitHub branch_protection API

Fixes sigmavirus24#1112

Since ~Q1 2022, branch_protection has an additional "checks" field which deprecates "contexts":
"contexts": list[str]
"checks": list[TypedDict("checks", context=str, app_id=int | None)]

The GitHub API returns both and then errors if both are present on update.

So, when making unrelated changes, check whether both are present and if so remove the "contexts" field, on the assumption that "checks" contains all the same data plus possibly app_id fields that we should not overwrite with nil.

Does this look OK? Happy to add polish, tests etc. if it's the right approach.

src/github3/repos/branch.py

@@ -437,6 +437,10 @@ def update(
                 else None
             ),
         }
+        if current_status["required_status_checks"] is not None and all(
+            key in current_status["required_status_checks"] for key in ("contexts", "checks")):
+            # Prefer the new "checks" field when updating
+            del current_status["required_status_checks"]["contexts"]
         edit = {
             "enabled": True,
             "enforce_admins": (
@@ -1186,7 +1190,7 @@ def delete_contexts(self, contexts):
         return self._boolean(resp, 204, 404)
 
     @decorators.requires_auth
-    def update(self, strict=None, contexts=None):
+    def update(self, strict=None, contexts=None, checks=None):
         """Update required status checks for the branch.
 
         This requires admin or owner permissions to the repository and
@@ -1201,6 +1205,10 @@ def update(self, strict=None, contexts=None):
             Whether this should be strict protection or not.
         :param list contexts:
             A list of context names that should be required.
+        :param list checks:
+            A list of dicts describing status checks that should be required.
+            Keys are: "context": str, "app_id": int (optional).
+            Replaces "contexts".
         :returns:
             A new instance of this class with the updated information
         :rtype:
@@ -1215,8 +1223,12 @@ def update(self, strict=None, contexts=None):
         json = None
         if strict is not None:
             update_data["strict"] = strict
-        if contexts is not None:
+        if contexts is not None and checks is not None:
+            raise ValueError("cannot supply both 'contexts' and 'checks'")
+        elif contexts is not None:
             update_data["contexts"] = contexts
+        elif checks is not None:
+            update_data["checks"] = checks
         if update_data:
             resp = self._patch(self.url, json=update_data)
             json = self._json(resp, 200)