Bug#564137: cachefile srcpkgcache.bin is discarded without good reason

[David Kalnischkies <kalnischkies+debian@gmail.com>]

Okay, i guess i have found it out:
In the cachefiles are not only Packages files but also the Translation files:
Which ones are downloaded are specified by the environment at update-time,
so e.g. LANG=de apt-get update will download Translation-de files and they
will be included in the srcpkgcache.bin file - so far so good.

Then the validness of the cache is checked the environment determines
again which Translation-file should be included in the cache:
So we have now two (similar) failure conditions:
a) The user has a different locale than root, so his Translation files are not
    included in the cache, leading to a discard.
b) A caller (like a cron-script) with LANG=C will encounter a cache with
   "too many" included files and discard it therefore as invalid.

a) is already a non-issue (non-existing is handled like empty ~
and the problem itself is hopefully fixed by the admin with the
config options coming in the next APT ABI-break)

b) is the offense here - for Translations ignoring the "too many"
shouldn't be a problem as the Translations are not used if they
have a non-requested languagecode ~ for other filetypes "too many"
is and will stay obviously a cache discarding reason.

I will look over the week into the code to find a suitable place to fix it.
Thanks so far to everyone involved! :)


Best regards / Mit freundlichen Grüßen,


David Kalnischkies