Well, it's just that the config and argument parsing is always the same, so the cachedir option is always checked the same way, no matter which operation is run.

But I agree the current behavior is a bit strange:
if a specified cachedir doesn't exist, pacman just fail
if no cachedir are specified, pacman will try to add the default one, /var/cache/pacman/pkg . But if this directory doesn't exist, the alpm_option_add_cachedir won't add it, and pacman will go on anyway, with an empty cachedir list (however, when the cachedir is actually needed, libalpm can fallback on /tmp)

And when the cachedir is actually needed (_alpm_filecache_setup function), it'll attempt to create the cachedir directories it they don't exist.
But this code is not reachable, since only existing directories can be added to the cachedir list using the alpm_option_add_cachedir function.

So either the directory creation in _alpm_filecache_setup could be removed, because it isn't used. Or the directory check in alpm_option_add_cachedir could be removed, because the directory can be created later by _alpm_filecache_setup.

How about this?

Yes, this apparently works, and reproduces the old 3.0 behavior as was requested.

Please test with the newest pacman-git build (pacman-git 20080105-1). It should be fixed.

Yes, this looks okay to me now. Feel free to close.