Consolidate GitHub helpers for community scripts (#63198)

It's been fun for a while to have the same function calling GitHub API
in every single script, but we're going to have fun in different ways
now.

This one's for you, @MrSubidubi! 🥂 

## Testing

I've ran the things that had `--dry-run` locally and nothing blew up,
but the ultimate smoke test will be carried out in production.

---

Release Notes:

- N/A

script/github_helpers.py

@@ -0,0 +1,214 @@
+import os
+import sys
+import time
+
+import requests
+
+GITHUB_API_URL = "https://api.github.com"
+RETRYABLE_STATUS_CODES = {429, 500, 502, 503, 504}
+MAX_ATTEMPTS = 4
+REQUEST_TIMEOUT_SECONDS = 30
+
+
+def _github_headers():
+    token = os.environ.get("GITHUB_TOKEN")
+    if not token:
+        raise RuntimeError("GITHUB_TOKEN environment variable is required")
+    return {
+        "Authorization": f"Bearer {token}",
+        "Accept": "application/vnd.github+json",
+        "X-GitHub-Api-Version": "2022-11-28",
+    }
+
+
+def _retry_delay(response, attempt):
+    retry_after = response.headers.get("Retry-After")
+    if retry_after:
+        try:
+            return max(float(retry_after), 0)
+        except ValueError:
+            pass
+    return 2**attempt
+
+
+def _github_request(method, path, *, params=None, body=None, retry=True):
+    url = f"{GITHUB_API_URL}/{path}"
+    max_attempts = MAX_ATTEMPTS if retry else 1
+    for attempt in range(max_attempts):
+        try:
+            response = requests.request(
+                method,
+                url,
+                headers=_github_headers(),
+                params=params,
+                json=body,
+                timeout=REQUEST_TIMEOUT_SECONDS,
+            )
+        except (requests.ConnectionError, requests.Timeout) as error:
+            if attempt == max_attempts - 1:
+                raise
+            delay = 2**attempt
+            print(
+                f"Transient GitHub API error ({error}); retrying in {delay}s",
+                file=sys.stderr,
+            )
+            time.sleep(delay)
+            continue
+
+        if (
+            response.status_code in RETRYABLE_STATUS_CODES
+            and attempt < max_attempts - 1
+        ):
+            delay = _retry_delay(response, attempt)
+            print(
+                f"GitHub API returned {response.status_code}; retrying in {delay}s",
+                file=sys.stderr,
+            )
+            time.sleep(delay)
+            continue
+
+        response.raise_for_status()
+        return response
+
+    raise RuntimeError("GitHub API retry loop exited without returning")
+
+
+def github_rest_api(method, path, params=None, body=None):
+    # Retrying writes after an ambiguous timeout can duplicate comments or mutations.
+    retry = method.upper() in {"GET", "HEAD", "OPTIONS"}
+    response = _github_request(
+        method, path, params=params, body=body, retry=retry
+    )
+    if response.status_code == 204 or not response.content:
+        return {}
+    return response.json()
+
+
+def github_rest_get_paginated(path):
+    results = []
+    page = 1
+    while True:
+        batch = github_rest_api(
+            "GET", path, params={"per_page": 100, "page": page}
+        )
+        if not batch:
+            return results
+        results.extend(batch)
+        if len(batch) < 100:
+            return results
+        page += 1
+
+
+def post_github_comment(owner, repository, issue_number, body):
+    github_rest_api(
+        "POST",
+        f"repos/{owner}/{repository}/issues/{issue_number}/comments",
+        body={"body": body},
+    )
+
+
+def github_graphql(query, variables=None, *, partial_errors_ok=False):
+    # GraphQL uses POST for reads and writes, so classify the operation before retrying.
+    retry = not query.lstrip().startswith("mutation")
+    response = _github_request(
+        "POST",
+        "graphql",
+        body={"query": query, "variables": variables or {}},
+        retry=retry,
+    )
+    result = response.json()
+    if "errors" in result:
+        if not partial_errors_ok or "data" not in result:
+            raise RuntimeError(f"GraphQL errors: {result['errors']}")
+        print(f"GraphQL partial errors (ignored): {result['errors']}", file=sys.stderr)
+    return result["data"]
+
+
+def fetch_github_project(project_number, owner="zed-industries"):
+    data = github_graphql(
+        """
+        query($owner: String!, $number: Int!) {
+          organization(login: $owner) {
+            projectV2(number: $number) {
+              id
+              fields(first: 50) {
+                nodes {
+                  ... on ProjectV2Field { id name dataType }
+                  ... on ProjectV2SingleSelectField { id name options { id name } }
+                }
+              }
+            }
+          }
+        }
+        """,
+        {"owner": owner, "number": project_number},
+    )
+    project = data["organization"]["projectV2"]
+    if not project:
+        raise RuntimeError(f"Project #{project_number} not found in {owner}")
+    return project
+
+
+def add_github_project_item(project_id, content_id):
+    data = github_graphql(
+        """
+        mutation($projectId: ID!, $contentId: ID!) {
+          addProjectV2ItemById(input: {projectId: $projectId, contentId: $contentId}) {
+            item { id }
+          }
+        }
+        """,
+        {"projectId": project_id, "contentId": content_id},
+    )
+    return data["addProjectV2ItemById"]["item"]["id"]
+
+
+def set_github_project_field(project, item_id, field_name, option_name):
+    field = next(
+        (field for field in project["fields"]["nodes"] if field.get("name") == field_name),
+        None,
+    )
+    if not field:
+        available = [
+            field["name"] for field in project["fields"]["nodes"] if "name" in field
+        ]
+        raise RuntimeError(
+            f"Field '{field_name}' not found on project. Available: {available}"
+        )
+
+    option_id = next(
+        (
+            option["id"]
+            for option in field.get("options", [])
+            if option["name"] == option_name
+        ),
+        None,
+    )
+    if not option_id:
+        available = [option["name"] for option in field.get("options", [])]
+        raise RuntimeError(
+            f"Option '{option_name}' not found in field '{field_name}'. "
+            f"Available: {available}"
+        )
+
+    github_graphql(
+        """
+        mutation($projectId: ID!, $itemId: ID!, $fieldId: ID!, $optionId: String!) {
+          updateProjectV2ItemFieldValue(input: {
+            projectId: $projectId
+            itemId: $itemId
+            fieldId: $fieldId
+            value: { singleSelectOptionId: $optionId }
+          }) {
+            projectV2Item { id }
+          }
+        }
+        """,
+        {
+            "projectId": project["id"],
+            "itemId": item_id,
+            "fieldId": field["id"],
+            "optionId": option_id,
+        },
+    )
+    print(f"Set '{field_name}' to '{option_name}'")