httpcache.Syncer interface: Fetch() (bool, error) — satisfied by both
*httpcache.Cacher and *gitshallow.Repo (new Fetch method + LightGC field).
httpcache.Cacher.Fetch now errors on zero-length 200 response instead of
clobbering the existing file with empty content.
Sources.Fetch/Init drop the lightGC param (baked into Repo.LightGC).
Sources.syncs []httpcache.Syncer replaces the separate git/httpInbound/
httpOutbound fields — Fetch iterates syncs uniformly, no more switch.
Sources itself satisfies httpcache.Syncer.
Top-layer callers (IPFilter) now drive all reloads directly after
Sync/Fetch return. gitshallow.Init now returns (bool, error).
httpcache drops Init and Sync — callers just call Fetch.
fs/dataset deleted — generic File[T] wrapper didn't earn its abstraction layer
gitshallow.ShallowRepo → Repo (redundant with package name)
gitshallow.Repo.Register(func() error) — callbacks fire after each sync
gitshallow.Repo.Init/Run — full lifecycle in one package
caller (check-ip-blacklist) holds atomic.Pointer[Cohort] directly
gitshallow: fix double-fetch (pull already fetches), drop redundant -C flags
gitdataset: split into GitDataset[T] (file+atomic) and GitRepo (git+multi-dataset)
- NewDataset for file-only use, AddDataset to register with a GitRepo
- one clone/fetch per repo regardless of how many datasets it has
ipcohort: split Cohort into hosts (sorted /32, binary search) + nets (CIDRs, linear)
- fixes false negatives when broad CIDRs (e.g. /8) precede specific entries
- fixes Parse() sort-before-copy order bug
- ReadAll always sorts; unsorted param removed (was dead code)
