Busy mirrors and CDNs routinely break bulk fetches: pooled keep-alive
connections get closed remotely ('error sending request'), downloads are
cut short (surfacing as bogus checksum mismatches), and index generations
momentarily drift from the Release file fetched moments before.
- shared client: short idle-pool timeout and TCP keepalive, and a
bounded-retry GET helper now used for index, Release, keyring and
Launchpad fetches (previously reqwest::get, which has no timeouts)
- downloads: retry the whole download, and check the content length so
truncation is reported as such instead of a checksum mismatch
- sources index: on a checksum mismatch against the Release file, retry
pinned to the exact listed generation via Debian's by-hash mechanism;
body-read errors are retried and reported per component instead of
aborting the whole lookup
vhaudiquet
3ed95725e4