Use OpenSSH's `ControlPersist` option instead of implementing an
approximation ourselves.  This avoids an infinite sleep in case the
`ssh` call fails and the socket never appears.

Rather than keying on the byhash boolean, make Release always a symlink
to zzz-dists.
Signed-off-by: NJulien Cristau <jcristau@debian.org>

The byhash boolean now controls:
- whether Release lives in zzz-dists (should we change this too?)
- whether Acquire-by-hash is advertised in Release

This should help speed up the second stage of mirroring.
Signed-off-by: NJulien Cristau <jcristau@debian.org>

This silences a warning from newer SQLAlchemy releases:

    SAWarning: Textual SQL expression '[...]' should be explicitly
    declared as text('[...]')

Making the same error when adding the file locally in /usr/share/dpkg
for testing doesn't help with noticing this.

That doesn't store original name/timestamp, with the latter meaning a
change even if there wasn't one in the input. Ought to help systems like
snapshot.

While not really relevant, this change stops `check-override` from
trying to sync the source package's override with every run (as the
priority continued to differ).

Signed-off-by: NChris Lamb <lamby@debian.org>

When uploading using scp, the mtime might be set to the time from the
uploader's host.  Especially for the upstream tarballs this might result
in a mtime a long time in the past and queued might remove the uploaded
files right away as stray files.

Note that this removal only happens when the file is not processed: for
example when the upstream tarball gets uploaded (with an old mtime) and
queued processes uploads and removes stray files before the .changes for
the upload including the "old" tarball arrives.

Automatic debug packages are not listed in the source's Package-List
field, but are considered NEW in suites without an associated debug
suite (e.g. jessie).

This should allow running a bit more in parallel.