New package for fetching files from HTTP with conditional-GET semantics
and a sidecar metadata file that persists ETag/Last-Modified across
restarts. Splits connection vs download timeouts, supports custom auth
headers (stripped on cross-origin redirect), and exposes sentinel errors
for callers branching on failure mode. Integration tests included.
New package for keeping a local mirror of a remote git repo via shallow
fetch+reset (not pull --ff-only, which loses force-pushed history). Adds
MaxAge gate via FETCH_HEAD mtime to skip redundant network calls under
concurrent callers, and a git-shallow-sync CLI. Includes integration
tests plus a force-push regression test.
