ci: add cache clearing to PR merges (#874)

* ci: add cache clearing to PR merges

* some renaming

* small change to force cache

* add manual run option

scripts/clear_cache.py

@@ -0,0 +1,58 @@
+#!/bin/python3
+
+# A simple script to clean caches matching a PR ID.
+#
+# Expects a GitHub token in the environment variables as GITHUB_TOKEN.
+
+import os
+import json
+import sys
+from urllib.error import HTTPError, URLError
+
+from urllib.request import Request, urlopen
+
+URL = "https://api.github.com/repos/ClementTsang/bottom/actions/caches"
+
+
+def cache_list_request(key):
+    request = Request(URL, method="GET")
+    request.add_header("Accept", "application/vnd.github+json")
+    request.add_header("Authorization", "Bearer {}".format(key))
+    return request
+
+
+def delete_cache_request(key, id):
+    request = Request("{}/{}".format(URL, id), method="DELETE")
+    request.add_header("Accept", "application/vnd.github+json")
+    request.add_header("Authorization", "Bearer {}".format(key))
+    return request
+
+
+def main():
+
+    args = sys.argv
+    env = os.environ
+
+    key = env["GITHUB_TOKEN"]
+    pr_id = args[1]
+    ref = "refs/pull/{}/merge".format(pr_id)
+
+    with urlopen(cache_list_request(key)) as response:
+        response = json.load(response)
+        caches = response["actions_caches"]
+        for cache in caches:
+            if cache["ref"] == ref:
+                id = cache["id"]
+                try:
+                    print("Deleting ID {}...".format(id))
+                    urlopen(delete_cache_request(key, id))
+                except HTTPError as e:
+                    print("HTTPError with delete, error code {}.".format(e.code))
+                except URLError as _:
+                    print("URLError with delete.")
+                else:
+                    print("Successfully deleted cache ID {}!".format(id))
+
+
+if __name__ == "__main__":
+    main()