Adjust dachs README on building images

Updated README to reflect changes in Dachs build process and repository options.

Author: chbrandt

dockerfiles/dachs/README.md

@@ -1,42 +1,28 @@
 # Dachs build
 
-> **DaCHS and Debian**
->
-> [DaCHS version 2.3 is now included in Debian Bullseye main/stable distribution.](https://packages.debian.org/bullseye/gavodachs2-server)
->
-> Accordingly, Dachs-on-Docker is now based on `debian:bullseye` image.
-
-
-### TL;DR
 At the simplest, building Dachs is done through:
 
 ```bash
 $ docker build -t dachs .
 $ docker run -it --name some-dachs -p 8080:8080 dachs
 ```
 
-This will create a container with the `latest` version of Dachs (using GAVO's repository),
-and then run it (exposing port 8080 to localhost).
-
-> This (default) container runs both _dachs-server_ and _postgres_.
+This will create a container with the latest stable version of Dachs,
+as available in Debian 'main' repository.
 
 
 ## Debian/GAVO repositories
 _Par défaut_, _dachs_ will be installed from debian-stable (main) repository.
 If you feel like -- or _need_ -- to install some upgrade or patch
 you can make use of Debian backports or GAVO's release/beta repositories.
-You specify those on the building of the containers.
 
 The (`build-arg`) option you have to set is `INSTALL_REPO` for that.
 `INSTALL_REPO` understands the following values:
-* `gavo`: _default_. Enables GAVO _release_ and _beta_ repositories. You get to check the bleeding edge.
-* `backports`: enables Debian `bullseye-backports`. You get major versions as upgrades;
-* `main`: . You'll have the same DaCHS for ~2 years;
+* `main`: This is the _default_. Stable, uses only Debian `main` repository;
+* `backports`: Enables Debian `backports`, you'll get major versions as upgrades;
+* `gavo/beta` (or `gavo`): Enables GAVO _release_ and _beta_ repositories. Minor or custom patches -- directly from the oven -- are here.
 
-> Defining `gavo`, `latest` or _non_ declaring `INSTALL_REPO` have the same effect:
-> to build the _latest_ images (i.e, _gavo_)
-
-The latest/gavo image:
+The latest gavo software:
 ```bash
 $ docker build --build-arg INSTALL_REPO='gavo' -t dachs:gavo .
 $ docker tag dachs:gavo dachs:latest
@@ -47,7 +33,11 @@ To build an image with _backports_ you will do:
 $ docker build --build-arg INSTALL_REPO='backports' -t dachs:backports .
 ```
 
-Likewise, to build an image with only what's in Debian `main` repo:
+To build an image with only what's in Debian `main` repo:
 ```bash
 $ docker build --build-arg INSTALL_REPO='main' -t dachs:main .
 ```
+or, equivalently:
+```bash
+$ docker build -t dachs:main .
+```