While Podman automatically populates /etc/passwd and /etc/group with
matching entries for the mapped host user, such a feature is missing
from Docker. Install libnss-unknown, which will return passwd entries of
the form "uid-1000" for all unknown UIDs, to avoid warnings and other
weird behaviour that may occur when running as an unnamed user.

`-o` must be passed to useradd now to allow non-unique user entries, as
with libnss-unknown, every UID is considered occupied.

To make the container behave the same regardless of the UIDs used
outside of the container, choose a UID that is unlikely to be used by
the user mounting their build directory the container. 100 should not
conflict with common defaults on Linux (min UID 1000) or MacOS X
(min UID 500). Conveniently, there is already a group "users" at GID
100, so creating a new group can be avoided.

Initialize the /gluon volume with the contents of /etc/skel.

[Matthias Schiffer: extend commit message]

The build process fails without that.

Co-authored-by: Tom Herbers <mail@tomherbers.de>

* add missing libelf-dev dependency (to build x86-64)
* remove subversion dependency
* add rsync dependency
* add ecdsautils to docs

- [Release notes](https://github.com/editorconfig-checker/editorconfig-checker/releases)
- [Commits](https://github.com/editorconfig-checker/editorconfig-checker/compare/2.6.0...2.7.0

)

Signed-off-by: Jan-Niklas Burfeind <git@aiyionpri.me>

Co-authored-by: Jan-Niklas Burfeind <git@aiyionpri.me>
version bump to 2.6.0
aligned indentation

`apt-get clean` clears out the local repository of retrieved package files.
It removes everything but the lock file from /var/cache/apt/archives/ and
/var/cache/apt/archives/partial/.

Co-authored-by: Vieno Hakkerinen <vieno@chemnitz.freifunk.net>

Updates the image to have a newer build environment, which is required
for some of the maintainer scripts.

Increases the image size from 414 to 545 MB.

Using `make container` or, if you don't have automake/gmake on your host
system, `./scripts/container.sh` will build an image for the current
branch your are on and drop you into a shell running inside a container
using that image.

From there all tooling required to work on Gluon is available.

Supports both podman (preferred) and docker.