Bug#848194: Want way to get Release (or InRelease) file from cache
On Tue, Mar 19, 2024 at 04:51:35PM +0000, Colin Watson wrote:
> Hi,
>
> I don't know if it helps or hinders this bug since I have rather
> different reasons from Ian, but I found myself looking at this bug today
> because I also wanted a way to get hold of an [In]Release file. The
> difference is that I'm not trying to get hold of it for a particular
> package, but for (roughly) a sources.list entry; but all my other
> requirements seem basically the same as Ian's. My use case is as
> follows, and you can tell me if it's too different to include in the
> same report:
>
> * In order to be able to implement an "import the contents of this
> repository into our database" task in debusine
> (https://freexian-team.pages.debian.net/debusine/), I want to
> discover which architectures are supported by a given suite in a
> repository, assuming that it has at least a Release file. And of
> course then I want to be able to fetch all the files, but at least
> that part isn't so hard.
>
> * If you already know which architectures you want, then this is easy.
> But if you want to ask the repository which architectures it
> supports, as far as I know the only sensible way is to consult the
> Release file.
>
> * Acquiring and verifying Release files correctly is, as I'm sure you
> know, challenging. I would like to avoid writing my own code to call
> gpgv in just the right way (again). I've been here before with
> #918304.
>
> * I'd hoped to use python-debian, but its GPG verification support is
> currently not as good as it should be (#710923) and in any case what
> you get from its Release file handling is not very helpful
> (#1067160).
>
> * So I looked at apt/python-apt. I know how to instantiate a temporary
> apt cache with its own configuration (in the manner of chdist(1), for
> instance), and if I could discover the available architectures after
> an initial fetch then I could call "apt-get update" a second time
> with APT::Architectures set and then I'd have everything. However,
> given a cache, I seem to be able to access basically everything
> _except_ for the Release file in documented ways. As mentioned in
> this bug, "apt-get indextargets" omits the Release file
Sorry I'm afraid this is not exposed in the apt code. There is only a
function to check which architectures are supported but you can't get
a list.
Meanwhile apt-get indextargets omits release files by design as they
are not indextargets, but uh metaindex targets.
python-apt omits bindings for ReleaseFile, there really should be
a Cache.release_files list of release file objects. You'd still need
to parse them yourself because we don't have the data in the cache
but that will get you most of the way there.
You may also for now rely on the file matching *Release in the lists
dir.
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