[littlenano]

Every git fetch that receives objects writes a new packfile, and nothing consolidates them in this workload:

• the loose-object gc --auto trigger never fires, because objects arrive packed (a mirror here has 0 loose objects);
• pack consolidation now goes through a multi-pack-index, which a plain git fetch never creates.

On the nixpkgs mirror this accumulated 34,701 packfiles over five months. Each fetch then had to open every pack, so a fetch that found new objects took 4–5 minutes of one core, and one was always running.

A single git repack --geometric=2 -d --write-midx fixes it, and is cheap enough to repeat:

19 packs -> 2 packs, 688 MB -> 652 MB, 10.7 s
single-object lookup 1.6 s -> 0.07 s
fetch 8-13 s (4.5 min when new objects appeared) -> 1 s

This adds services.commit-notifier.maintenance (enabled by default): a oneshot service running that repack over /var/lib/commit-notifier/repositories/*/repo, scheduled by OnCalendar = cfg.maintenance.calendar (default daily) with Persistent and a randomised delay, as the commit-notifier user with Nice = 10 and idle I/O scheduling so it does not compete with the fetches.

[mergify]

Queued — the merge queue status continues in this comment ↓.

[mergify]

Merge Queue Status

• ✅ Entered queue — 2026-10-22 07:37 UTC · Rule: default · triggered by @linyinfeng with the merge queue checkbox
• ✅ Checks passed · on draft merge queue: checking #24 on main (8a6c37e) #25
• ✅ Merged — 2026-10-22 07:38 UTC · at bceca5e3590bf5f84f84872215a7bc4fb9baae2c · rebase

This pull request spent 1 minute 16 seconds in the queue, including 32 seconds running CI.

Required conditions to merge

• #check-failure = 0
• check-success = check