Merge carbon-project-tools back into carbon-lang (#203)

As proposed at https://forums.carbon-lang.dev/t/merged-repo-structure/174:

- carbon-lang:/src/jekyll -> carbon-lang:/website/jekyll
- carbon-lang:/src/scripts -> carbon-lang:/proposals/scripts
- carbon-project-tools:/firebase -> carbon-lang:/website/firebase
- carbon-project-tools:/github -> carbon-lang:/github

github/github_helpers.py

@@ -0,0 +1,102 @@
+"""GitHub GraphQL helpers.
+
+https://developer.github.com/v4/explorer/ is very useful for building queries.
+"""
+
+__copyright__ = """
+Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+Exceptions. See /LICENSE for license information.
+SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+"""
+
+import os
+
+# https://pypi.org/project/gql/
+import gql
+import gql.transport.requests
+
+_ENV_TOKEN = "GITHUB_ACCESS_TOKEN"
+
+# Query elements for pagination.
+PAGINATION = """pageInfo {
+  hasNextPage
+  endCursor
+}
+totalCount"""
+
+
+def add_access_token_arg(parser, permissions):
+    """Adds a flag to set the access token."""
+    access_token = os.environ.get(_ENV_TOKEN, default=None)
+    parser.add_argument(
+        "--access-token",
+        metavar="ACCESS_TOKEN",
+        default=access_token,
+        required=not access_token,
+        help="The access token for use with GitHub. May also be specified in "
+        "the environment as %s. The access token should have permissions: %s"
+        % (_ENV_TOKEN, permissions),
+    )
+
+
+class Client(object):
+    """A GitHub GraphQL client."""
+
+    def __init__(self, parsed_args):
+        """Connects to GitHub."""
+        transport = gql.transport.requests.RequestsHTTPTransport(
+            url="https://api.github.com/graphql",
+            headers={"Authorization": "bearer %s" % parsed_args.access_token},
+        )
+        self._client = gql.Client(
+            transport=transport, fetch_schema_from_transport=True
+        )
+
+    def execute(self, query):
+        """Runs a query."""
+        return self._client.execute(gql.gql(query))
+
+    def execute_and_paginate(self, query, path, first_page=None):
+        """Runs a query with pagination.
+
+        Arguments:
+          query: The GraphQL query template, which must have both 'cursor' and
+            'pagination' fields to fill in. The cursor should be part of the
+            location query (with 'first'), and the pagination should be at the
+            same level as nodes.
+          path: A list of strings indicating the path to the nodes in the
+            result.
+          first_page: An optional object for the first page of results, which
+            will otherwise automatically be collected. This exists for callers
+            to optimize by collecting other data with the first page.
+        """
+        format = {"cursor": "", "pagination": PAGINATION}
+        count = 0
+        exp_count = None
+        while True:
+            if first_page:
+                result = first_page
+                first_page = None
+            else:
+                result = self.execute(query % format)
+            # Follow the path to the nodes being paginated.
+            node_parent = result
+            for entry in path:
+                node_parent = node_parent[entry]
+            # Store the total count of responses.
+            if not exp_count:
+                exp_count = node_parent["totalCount"]
+            # Yield each node individually.
+            for node in node_parent["nodes"]:
+                yield node
+                count += 1
+            # Check for pagination, verifying the total count on exit.
+            page_info = node_parent["pageInfo"]
+            if not page_info["hasNextPage"]:
+                assert exp_count == count, "exp %d != actual %d at path %s" % (
+                    exp_count,
+                    count,
+                    path,
+                )
+                return
+            format["cursor"] = ' after: "%s"' % page_info["endCursor"]