add GitLab CI for linter

This adds a pipeline for using linters. Only flake8 is used for now.

alpine/flake8 doesn't start a shell but rather execute flake8 directly.
However, GitLab CI seems to start all containers by trying to start a
shell:

```
-c if [ -x /usr/local/bin/bash ]; then
	exec /usr/local/bin/bash
elif [ -x /usr/bin/bash ]; then
	exec /usr/bin/bash
elif [ -x /bin/bash ]; then
	exec /bin/bash
elif [ -x /usr/local/bin/sh ]; then
	exec /usr/local/bin/sh
elif [ -x /usr/bin/sh ]; then
	exec /usr/bin/sh
elif [ -x /bin/sh ]; then
	exec /bin/sh
elif [ -x /busybox/sh ]; then
	exec /busybox/sh
else
	echo shell not found
	exit 1
fi
```

Since flake8 is the entrypoint, it gets passed this long string which it
cannot do anything with (as opposed to the - I guess - expected `sh`).

Instead, let's replace the entrypoint of the docker image so that the
runner directly passes the script to the container.

Signed-off-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
new file mode 100644
index 0000000..47fd843
--- /dev/null
+++ b/.gitlab-ci.yml
@@ -0,0 +1,11 @@
+stages:
+  - linting
+
+flake8:
+  tags:
+    - docker
+  stage: linting
+  image:
+    name: docker.io/alpine/flake8:6.0.0
+    entrypoint: [""]
+  script: flake8 .