Add a --repository flag taking the full suite URL of an external flat
repository (e.g. https://pkg.noctalia.dev/deb/resolute/), i.e. one with
no dists/ hierarchy, like apt's exact-path suites ('Suites: resolute/').
The suite name is read from the root Release file (Codename/Suite), the
sources index is fetched from the repository root as Sources.xz/gz/plain,
and package files are resolved against the URL root, ignoring the stanza
Directory field like apt does. As with PPAs, the stanza Vcs-Git is never
used for external repositories, so the source always comes from the
repository itself.
Also make the sources index parser detect compression by magic bytes
(gz/xz/plain) instead of assuming gzip, and fix extraction of archives
with './'-prefixed entries, which previously aborted and are now
extracted in place instead of being relocated.
vhaudiquet
5500f98586