metadata sharing

[cgwalters]

There are multiple programs which consume librepo, such as PackageKit, dnf, and others.

However, there's no easy mechanism for these programs to share repository metadata. Two possible options:

• Define a shared directory /var/cache/librepo with rules for access (e.g. PackageKit/libhif style atomic swap)
• Have each program look in the other's directories for newer files (e.g. PackageKit looks at /var/cache/dnf, dnf looks at /var/cache/PackageKit
• Create a higher level library shared between the programs

Other options?

[hughsie]

I think a KISS solution would work here; i.e. just get librepo to look for local files in other places before re-downloading them. It would be a very small list of places to look, and 3 stat's + hardlink would be much cheaper and faster than downloading again and again.