- ProxyCached now stores upstream Last-Modified in the cache and uses it
(along with ETag) for conditional request handling, returning 304 when
client validators match. Adds Content-Length to cached responses.
- Handlers calling FetchOrCacheMetadata (pypi, composer, pub, nuget) now
check for ErrUpstreamNotFound and return 404 instead of 502, matching
the existing npm and cargo behavior.
- Mirror jobs report live progress via a periodic callback while running,
so API polls return real counts instead of zeroed progress.
- Registry mirroring removed from CLI flags, API acceptance, README, and
docs since every enumerator was a stub returning "not yet implemented".
- Added tests for the conditional metadata path (ETag/If-None-Match,
Last-Modified/If-Modified-Since, 304 responses, header omission).
Add a `proxy mirror` CLI command and `/api/mirror` API endpoints that
pre-populate the cache from various input sources: individual PURLs,
SBOM files (CycloneDX and SPDX), or full registry enumeration.
The mirror reuses the existing handler.Proxy.GetOrFetchArtifact()
pipeline so cached artifacts are identical to those fetched on demand.
A bounded worker pool controls download parallelism.
Metadata caching is opt-in via `cache_metadata: true` in config (or
PROXY_CACHE_METADATA=true). The mirror command always enables it. When
enabled, upstream metadata responses are stored for offline fallback
with ETag-based conditional revalidation.
New internal/mirror package with Source interface, PURLSource,
SBOMSource, RegistrySource, and async JobStore. New metadata_cache
database table for offline metadata serving.
