GitHub throttles packfile generation for this repository with
repo-scoped HTTP 429s that are not client IP rate limits: an
anonymous clone of a small repo succeeds and the API quota is
untouched, but the single big pack behind --depth 1 dies
mid-transfer with 'RPC failed; HTTP 429 / expected packfile'. The
fresh-install clone path had no retry and no fallback, so a clean
machine exited 1 at the download stage and left a half-populated
install directory (same throttle as the update path in #89287).
Retry the HTTPS clone with linear backoff, removing the partial
clone between attempts; when every direct attempt fails, degrade
to a blobless partial clone and materialize the working tree with
a hard reset — many small packs instead of one big one, which is
what gets past the throttle. SSH-first ordering, the existing
installation update branch, and the commit-pin flow are unchanged.
11afd07f16