Add new stage for configuring DNF Automatic

Add a new stage `org.osbuild.dnf-automatic.config` for configuring DNF
Automatic.

The stage changes persistent DNF Automatic configuration. Currently, only
a subset of options can be set:
  - 'commands' section
    - apply_updates
    - upgrade_type

Fix #908

Signed-off-by: Tomas Hozza <thozza@redhat.com>

stages/org.osbuild.dnf-automatic.config

@@ -0,0 +1,92 @@
+#!/usr/bin/python3
+"""
+Change DNF Automatic configuration.
+
+The stage changes persistent DNF Automatic configuration. Currently, only
+a subset of options can be set:
+  - 'commands' section
+    - apply_updates
+    - upgrade_type
+"""
+
+
+import sys
+import iniparse
+
+import osbuild.api
+
+
+SCHEMA = r"""
+"definitions": {
+  "commands": {
+    "type": "object",
+    "additionalProperties": false,
+    "description": "'commands' configuration section.",
+    "properties": {
+      "apply_updates": {
+        "type": "boolean",
+        "description": "Whether packages comprising the available updates should be installed."
+      },
+      "upgrade_type": {
+        "type": "string",
+        "description": "What kind of upgrades to look at.",
+        "enum": ["default", "security"]
+      }
+    }
+  }
+},
+"additionalProperties": false,
+"description": "DNF Automatic configuration.",
+"properties": {
+  "config": {
+    "type": "object",
+    "additionalProperties": false,
+    "description": "configuration definition.",
+    "properties": {
+      "commands": {
+        "$ref": "#/definitions/commands"
+      }
+    }
+  }
+}
+"""
+
+
+def bool_to_yes_no(b):
+    if b:
+        return "yes"
+    return "no"
+
+
+def main(tree, options):
+    config = options.get("config")
+    dnf_automatic_config_path = f"{tree}/etc/dnf/automatic.conf"
+    dnf_automatic_conf = iniparse.SafeConfigParser()
+
+    # do not touch the config file if not needed
+    if config is None:
+        return 0
+
+    try:
+        with open(dnf_automatic_config_path, "r") as f:
+            dnf_automatic_conf.readfp(f)
+    except FileNotFoundError:
+        print(f"Error: DNF automatic configuration file '{dnf_automatic_config_path}' does not exist.")
+        return 1
+
+    for config_section, config_options in config.items():
+        for option, value in config_options.items():
+            if isinstance(value, bool):
+                value = bool_to_yes_no(value)
+            dnf_automatic_conf.set(config_section, option, value)
+
+    with open(dnf_automatic_config_path, "w") as f:
+        dnf_automatic_conf.write(f)
+
+    return 0
+
+
+if __name__ == '__main__':
+    args = osbuild.api.arguments()
+    r = main(args["tree"], args["options"])
+    sys.exit(r)