ci: Export the container id in python script

This refactor does not change behavior, but it has a few benefits:

* The shellcheck SC2086 warning is disabled for the whole command, but
  is only needed for the CI_CONTAINER_CAP env var. So in Python, only
  pass this one env var to shlex.split() for proper word splitting.
* Future logic improvements can be implemented in Python.

The comments are moved, which can be checked via the git options:
--color-moved=dimmed-zebra --color-moved-ws=ignore-all-space

ci/test/02_run_container.py

@@ -3,6 +3,7 @@
 # Distributed under the MIT software license, see the accompanying
 # file COPYING or https://opensource.org/license/mit/.
 
+from pathlib import Path
 import os
 import shlex
 import subprocess
@@ -71,6 +72,79 @@ def main():
             time.sleep(3)
             run(cmd_build)
 
+        for suffix in ["ccache", "depends", "depends_sources", "previous_releases"]:
+            run(["docker", "volume", "create", f"{os.environ['CONTAINER_NAME']}_{suffix}"], check=False)
+
+        CI_CCACHE_MOUNT = f"type=volume,src={os.environ['CONTAINER_NAME']}_ccache,dst={os.environ['CCACHE_DIR']}"
+        CI_DEPENDS_MOUNT = f"type=volume,src={os.environ['CONTAINER_NAME']}_depends,dst={os.environ['DEPENDS_DIR']}/built"
+        CI_DEPENDS_SOURCES_MOUNT = f"type=volume,src={os.environ['CONTAINER_NAME']}_depends_sources,dst={os.environ['DEPENDS_DIR']}/sources"
+        CI_PREVIOUS_RELEASES_MOUNT = f"type=volume,src={os.environ['CONTAINER_NAME']}_previous_releases,dst={os.environ['PREVIOUS_RELEASES_DIR']}"
+        CI_BUILD_MOUNT = []
+
+        if os.getenv("DANGER_CI_ON_HOST_FOLDERS"):
+            # ensure the directories exist
+            for create_dir in [
+                    os.environ["CCACHE_DIR"],
+                    f"{os.environ['DEPENDS_DIR']}/built",
+                    f"{os.environ['DEPENDS_DIR']}/sources",
+                    os.environ["PREVIOUS_RELEASES_DIR"],
+                    os.environ["BASE_BUILD_DIR"],  # Unset by default, must be defined externally
+            ]:
+                Path(create_dir).mkdir(parents=True, exist_ok=True)
+
+            CI_CCACHE_MOUNT = f"type=bind,src={os.environ['CCACHE_DIR']},dst={os.environ['CCACHE_DIR']}"
+            CI_DEPENDS_MOUNT = f"type=bind,src={os.environ['DEPENDS_DIR']}/built,dst={os.environ['DEPENDS_DIR']}/built"
+            CI_DEPENDS_SOURCES_MOUNT = f"type=bind,src={os.environ['DEPENDS_DIR']}/sources,dst={os.environ['DEPENDS_DIR']}/sources"
+            CI_PREVIOUS_RELEASES_MOUNT = f"type=bind,src={os.environ['PREVIOUS_RELEASES_DIR']},dst={os.environ['PREVIOUS_RELEASES_DIR']}"
+            CI_BUILD_MOUNT = [f"--mount=type=bind,src={os.environ['BASE_BUILD_DIR']},dst={os.environ['BASE_BUILD_DIR']}"]
+
+        if os.getenv("DANGER_CI_ON_HOST_CCACHE_FOLDER"):
+            if not os.path.isdir(os.environ["CCACHE_DIR"]):
+                print(f"Error: Directory '{os.environ['CCACHE_DIR']}' must be created in advance.")
+                sys.exit(1)
+            CI_CCACHE_MOUNT = f"type=bind,src={os.environ['CCACHE_DIR']},dst={os.environ['CCACHE_DIR']}"
+
+        run(["docker", "network", "create", "--ipv6", "--subnet", "1111:1111::/112", "ci-ip6net"], check=False)
+
+        if os.getenv("RESTART_CI_DOCKER_BEFORE_RUN"):
+            print("Restart docker before run to stop and clear all containers started with --rm")
+            run(["podman", "container", "rm", "--force", "--all"])  # Similar to "systemctl restart docker"
+
+            # Still prune everything in case the filtered pruning doesn't work, or if labels were not set
+            # on a previous run. Belt and suspenders approach, should be fine to remove in the future.
+            # Prune images used by --external containers (e.g. build containers) when
+            # using podman.
+            print("Prune all dangling images")
+            run(["podman", "image", "prune", "--force", "--external"])
+
+        print(f"Prune all dangling {CI_IMAGE_LABEL} images")
+        # When detecting podman-docker, `--external` should be added.
+        run(["docker", "image", "prune", "--force", "--filter", f"label={CI_IMAGE_LABEL}"])
+
+        cmd_run = ["docker", "run", "--rm", "--interactive", "--detach", "--tty"]
+        cmd_run += [
+            "--cap-add=LINUX_IMMUTABLE",
+            *shlex.split(os.getenv("CI_CONTAINER_CAP", "")),
+            f"--mount=type=bind,src={os.environ['BASE_READ_ONLY_DIR']},dst={os.environ['BASE_READ_ONLY_DIR']},readonly",
+            f"--mount={CI_CCACHE_MOUNT}",
+            f"--mount={CI_DEPENDS_MOUNT}",
+            f"--mount={CI_DEPENDS_SOURCES_MOUNT}",
+            f"--mount={CI_PREVIOUS_RELEASES_MOUNT}",
+            *CI_BUILD_MOUNT,
+            f"--env-file={env_file}",
+            f"--name={os.environ['CONTAINER_NAME']}",
+            "--network=ci-ip6net",
+            f"--platform={os.environ['CI_IMAGE_PLATFORM']}",
+            os.environ["CONTAINER_NAME"],
+        ]
+
+        container_id = run(
+            cmd_run,
+            stdout=subprocess.PIPE,
+            text=True,
+        ).stdout.strip()
+        os.environ["CI_CONTAINER_ID"] = container_id
+
     run(["./ci/test/02_run_container.sh"])  # run the remainder