allow a method to request auxiliary files

If a method needs a file to operate like e.g. mirror needs to get a list
of mirrors before it can redirect the the actual requests to them. That
could easily be solved by moving the logic into libapt directly, but by
allowing a method to request other methods to do something we can keep
this logic contained in the method and allow e.g. also methods which
perform binary patching or similar things.

Previously they would need to implement their own acquire system inside
the existing one which in all likelyhood will not support the same
features and methods nor operate with similar security compared to what
we have already running 'above' the requesting method. That said, to
avoid methods producing conflicts with "proper" files we are downloading
a new directory is introduced to keep the auxiliary files in.

[The message magic number 351 is a tribute to the german Grundgesetz
article 35 paragraph 1 which defines that all authorities of the
state(s) help each other on request.]

1 files changed, 2 insertions, 1 deletions

diff --git a/test/integration/test-ubuntu-bug-346386-apt-get-update-paywall b/test/integration/test-ubuntu-bug-346386-apt-get-update-paywall
index 3571a9f25..5f2109db9 100755
--- a/test/integration/test-ubuntu-bug-346386-apt-get-update-paywall
+++ b/test/integration/test-ubuntu-bug-346386-apt-get-update-paywall
@@ -41,7 +41,8 @@ runtests() {
 	testsuccess grep "$1" rootdir/tmp/testfailure.output
 
 	ensure_n_canary_strings_in_dir "$LISTS" 'ni ni ni' 0
-	testequal 'lock
+	testequal 'auxfiles
+lock
 partial' ls "$LISTS"
 
 	# and again with pre-existing files with "valid data" which should remain