Fix the WPT export script

- Have the WPT exporter script use the WPT_SYNC_TOKEN for checking out
  wpt.
- Make sure the local WPT repository is unshallow when pushing.
- When searching for existing PRs use the main GitHub search API,
  as the pull request search does not seem to properly process
  the "head" parameter.
- When deleting branches in the downstream WPT repository, use
  the full URL to avoid trying to modify the upstream repository.

.github/workflows/upstream-wpt-changes.yml

@@ -25,7 +25,12 @@ jobs:
         with:
           path: wpt
           repository: 'web-platform-tests/wpt'
-          token: ${{ secrets.GITHUB_TOKEN }}
+          # The token here must be the token that we will use to push to the
+          # WPT repository and not the token used for GitHub actions, because
+          # the checkout action sets up an `extraheader` authorization override
+          # using the token specified here.
+          # See https://github.com/actions/checkout/issues/162.
+          token: ${{ secrets.WPT_SYNC_TOKEN }}
       - name: Install requirements
         run: pip install -r servo/etc/ci/upstream-wpt-changes/requirements.txt
       - name: Process pull request

etc/ci/upstream-wpt-changes/test.py

@@ -131,12 +131,29 @@ class MockGitHubAPIServer():
                     return ('', 204)
             return ('', 404)
 
-        @self.app.route("/repos/<org>/<repo>/pulls", methods=['GET'])
-        def get_pulls(org, repo):
+        @self.app.route("/search/issues", methods=['GET'])
+        def search():
+            params = {}
+            param_strings = flask.request.args.get("q", "").split(" ")
+            for string in param_strings:
+                parts = string.split(":")
+                params[parts[0]] = parts[1]
+
+            assert params["is"] == "pr"
+            assert params["state"] == "open"
+            assert "author" in params
+            assert "head" in params
+            head_ref = f"{params['author']}:{params['head']}"
+
             for pull_request in self.pulls:
-                if pull_request.head == flask.request.args["head"]:
-                    return json.dumps([{"number": pull_request.number}])
-            return json.dumps([])
+                if pull_request.head == head_ref:
+                    return json.dumps({
+                        "total_count": 1,
+                        "items": [{
+                            "number": pull_request.number
+                        }]
+                    })
+            return json.dumps({"total_count": 0, "items": []})
 
         @self.app.route("/repos/<org>/<repo>/pulls", methods=['POST'])
         def create_pull_request(org, repo):

etc/ci/upstream-wpt-changes/wptupstreamer/github.py

@@ -76,18 +76,30 @@ class GithubRepository:
         """If this repository has an open pull request with the
         given source head reference targeting the master branch,
         return the first matching pull request, otherwise return None."""
-        # Frustratingly, this is different from what you need for opening a pull request.
-        head = f"{branch.repo.org}:{branch.name}"
-        response = authenticated(
-            self.sync, "GET", f"{self.pulls_url}?head={head}&base=master&state=open"
-        )
+
+        params = "+".join([
+            "is:pr",
+            "state:open",
+            f"repo:{self.repo}",
+            f"author:{branch.repo.org}",
+            f"head:{branch.name}",
+        ])
+        response = authenticated(self.sync, "GET", f"search/issues?q={params}")
         if int(response.status_code / 100) != 2:
             return None
 
         json = response.json()
-        if not json or not isinstance(json, list):
+        if not isinstance(json, dict) or \
+           "total_count" not in json or \
+           "items" not in json:
+            raise ValueError(
+                f"Got unexpected response from GitHub search: {response.text}"
+            )
+
+        if json["total_count"] < 1:
             return None
-        return self.get_pull_request(json[0]["number"])
+
+        return self.get_pull_request(json["items"][0]["number"])
 
     def open_pull_request(self, branch: GithubBranch, title: str, body: str):
         data = {

etc/ci/upstream-wpt-changes/wptupstreamer/step.py

@@ -172,6 +172,12 @@ class CreateOrUpdateBranchForPRStep(Step):
 
             # Push the branch upstream (forcing to overwrite any existing changes).
             if not run.sync.suppress_force_push:
+
+                # In order to push to our downstream branch we need to ensure that
+                # the local repository isn't a shallow clone. Shallow clones are
+                # commonly created by GitHub actions.
+                run.sync.local_wpt_repo.run("fetch", "--unshallow", "origin")
+
                 user = run.sync.github_username
                 token = run.sync.github_api_token
                 repo = run.sync.downstream_wpt_repo
@@ -198,7 +204,11 @@ class RemoveBranchForPRStep(Step):
         self.name += f":{run.sync.downstream_wpt.get_branch(self.branch_name)}"
         logging.info("  -> Removing branch used for upstream PR")
         if not run.sync.suppress_force_push:
-            run.sync.local_wpt_repo.run("push", "origin", "--delete",
+            user = run.sync.github_username
+            token = run.sync.github_api_token
+            repo = run.sync.downstream_wpt_repo
+            remote_url = f"https://{user}:{token}@github.com/{repo}.git"
+            run.sync.local_wpt_repo.run("push", remote_url, "--delete",
                                         self.branch_name)