local install with apt-get still producing caches in /var/lib/dpkg/{info,alternatives,info, ...}

[Albretch Mueller <lbrtchx@gmail.com>]

~
 After taking snapshots of my file system before and after
installations using apt-get, I noticed lots of files in:
~
/var/lib/dpkg/{info,alternatives,info, ...}
~
 relating to the files I installed, but those files I had grabbed
locally like this:
~
_SL=<some partial local repo/directory>
apt-get update -o Dir::Etc::SourceList=${_SL}
apt-get install -y -V -o Dir::Etc::SourceList=${_SL} kate
~
 dpkg does have an admindir option to set the temporary local cache
~
# dpkg --help | grep admindir
  --admindir=<directory>     Use <directory> instead of /var/lib/dpkg.
~
 but I don't see an "admindir" option in apt-get
~
# apt-get --help | grep admindir
# apt-get --help | grep admin
# apt-get --help | grep var
~
 and apt-get(8) does not say a thing about caching files at:
~
 /var/lib/dpkg
~
 I am not using dpkg to any install packages, just to list installed
packages a la:
~
 dpkg -l > dpkg00.txt
~
 using the "clean" option of apt-get may delete the deb installation
files I do keep locally
~
 How do I set the "/var/lib/dpkg" directory to be used by apt-get?
~
 How is it being set to beging with if I don't explicitly use dpkg to
install packages?
~
 Thank you
 lbrtchx