sbuild and trivial local repository

[PICCA Frederic-Emmanuel <frederic-emmanuel.picca@synchrotron-soleil.fr>]

Hello, I try to write a really simple script in perl which allows me to rebuild a bunch of packages using a file with a really simple syntax

backport hkl
git haskell-hkl https://repo.or.cz/hkl.git contrib/haskell
...

I setup a chroot with the sbuild-debian-developer-setup -> ok

Now I can build packages with the sbuild command from a checkout package -> ok

Now I need to keep the generated packages to build the next one.
So I want to setup a local repository own by the user `/home/<user>/repository`
I use apt-ftparchive in order to maintain the Packages, Sources and Release file between each package build. -> ok

My problem is: how can I bind the local repository into the chroot via sbuild.

I understand that I can put this configuration in the /etc/schroot/sbuild/fstab configuration.

/home/user/repository /tmp/repository none rw,bind 0 0

but the user repository path  is a moving target.

So my question is

how can I do this mount from the sbuild command line

thanks

Frederic