Update location of the Contents files on the mirrors

[Niels Thykier]

Debian and Ubuntu currently do not agree on where to place the "Contents" files on the mirror.

 * Debian places them in the component, a la:
   - $SUITE/$COMPONENT/Contents-$ARCH

 * Ubuntu places them next to the "InRelease" file:
   - $SUITE/Contents-$ARCH

Note that the Debian variant only contains the file names for packages in the given component, where as Ubuntu's (presumably) contain the file names for all packages in the suite.

There is an open question on making this backwards compatible. Currently, apt-file is patched to use the path on the Ubuntu mirrors when it is merged into Ubuntu (apt-file/3.0 still needs a diff here, albeit "only" a configuration change).

 * I had a conversation with DonKult (APT maintainer) about making APT able to support "alternative" download locations (in #debian-deity on OFTC).
 * If implemented, apt + apt-file/3.X could support the Ubuntu and the Debian location at the same time.

Related topics: Contents-all is supported by apt-file/3.0 (don't remember if APT can be told to fetch it though). It might be worth investigating separating the "arch:all" parts from Contents-$ARCH at the same time.

NB: Colin Watson suggested I filed this a bug against launchpad.

[Niels Thykier (niels-thykier)]

Re: Contents-all: Very recent versions of apt and apt-file should be ready for this. See https://wiki.debian.org/RepositoryFormat#No-Support-for-Architecture-all for how to declare the Contents-all file being split.

[Niels Thykier (niels-thykier)]

The following commits where just pushed to APT's master branch:
 * https://anonscm.debian.org/cgit/apt/apt.git/commit/?id=7f2d1ee
 * https://anonscm.debian.org/cgit/apt/apt.git/commit/?id=39c724b

These looks very promising IRT making apt-file support both locations at the same time. :)

[Jeremy Bícha (jbicha)]

See LP: #1697120

[Niels Thykier (niels-thykier)]

For reference, apt-file 3 will now prefer the "$SUITE/$COMPONENT/Contents-$ARCH" location over "$SUITE/Contents-$ARCH". If launchpad provides both locations, it should work for apt-file 2 (in older releases) and apt-file 3 (artful and later). At the same time, it would also fix LP: #1697120 (currently filed against apt-file 3).