first version with test
add unittest for new sourceslist parser as well
fix section adding
first version with test
add unittest for new sourceslist parser as well
fix section adding
refactor deb822 reading into its own function
more refactor
add APT::Sources::Use-Deb822 to allow disabling the deb822 parser
suppoer $(ARCH) in deb822 sources.list as well
Merge remote-tracking branch 'origin/feature/deb-src-bts731102' into feature/source-deb822
Merge remote-tracking branch 'upstream/debian/sid' into feature/source-deb822
Merge remote-tracking branch 'origin/feature/source-deb822' into feature/source-deb822

Conflicts:
	apt-pkg/sourcelist.cc
query an empty pkgAcqIndexDiffs if index is up-to-date

The previous code already did this, this is just being a hell of a lot
more obvious, so that it isn't that easy to break in the future.

Git-Dch: Ignore
allow ':' in GetListOfFilesInDir

run-parts doesn't allow this char in valid filenames, but we tend to
have files with this character in e.g. /var/lib/apt/lists/

Git-Dch: Ignore
implement POC client-side merging of pdiffs via apt-file

The idea of pdiffs is to avoid downloading the hole file by patching the
existing index. This works very well, but becomes slow if a lot of
patches needs to be applied to reconstruct an up-to-date index and in
recent years more and more dinstall (or similar) runs are executed
creating more and more pdiffs in the same amount of time, so pdiffs
became less useful.

The solution is simple: Reduce the amount of patches (which are very
small) which need to be applied on top of the index we have available
(which is usually pretty big).

This can be done in two ways: Either merge the patches on the
server-side so that the client has to download only one patch or the
patches are all downloaded and merged on the client-side.

The first needs a client who is doing one step at a time who can also
skip patches if it needs (APT supports this for a long time now).

The later is implemented by this commit, but depends on the server NOT
merging the patches and the patches being in a strict order in which no
patch is skipped.

This is traditionally the case for dak, but other repository creators
support merging – e.g. reprepro (which helpfully adds a flag indicating
that the patches are merged). To support both or even mixes a client
needs more information which isn't available for now.

This POC uses the external diffindex-rred included in apt-file to
do the heavy lifting of merging & applying all patches in one pass,
hence to test this feature apt-file needs to be installed.
Merge branch 'debian/sid' into feature/source-deb822
Merge branch 'debian/sid' into feature/source-deb822
improve tests
improve error message