Add new stage for creating YUM / DNF repo files

Add a new stage `org.osbuild.yum.repos` for creating YUM / DNF `.repo`
files in `/etc/yum.repos.d`. All repo-specific options are supported but
only a subset of options which can be set for a repo as well as in the
[main] section are supported.

Add unit test for the new stage.

Fix #907

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

stages/org.osbuild.yum.repos

@@ -0,0 +1,193 @@
+#!/usr/bin/python3
+"""
+Create YUM / DNF repo file in /etc/yum.repos.d
+
+All repo-specific options, except the 'type' option, are supported. The 'type'
+repo options is not supported, since it accepts only a single value, therefore
+the ability to set it adds no value.
+
+Only a subset of options which can be used in both, a repo or [main] section
+configuration, is supported, specifically:
+  - gpgcheck
+  - repo_gpgcheck
+"""
+
+import os
+import sys
+import configparser
+
+import osbuild.api
+
+
+SCHEMA = r"""
+"definitions": {
+  "repo": {
+    "type": "object",
+    "additionalProperties": false,
+    "oneOf": [
+      {
+        "required": ["id", "baseurl"]
+      },
+      {
+        "required": ["id", "metalink"]
+      },
+      {
+        "required": ["id", "mirrorlist"]
+      }
+    ],
+    "description": "YUM / DNF repo definition.",
+    "properties": {
+      "id": {
+        "type": "string",
+        "description": "Repository ID.",
+        "pattern": "^[\\w.\\-:]+$"
+      },
+      "baseurl": {
+        "type": "array",
+        "description": "List of URLs for the repository.",
+        "minItems": 1,
+        "items": {
+          "type": "string",
+          "minLength": 1
+        }
+      },
+      "cost": {
+        "type": "integer",
+        "description": "The  relative  cost of accessing this repository, defaulting to 1000."
+      },
+      "enabled": {
+        "type": "boolean",
+        "description": "Include this repository as a package source."
+      },
+      "gpgkey": {
+        "type": "array",
+        "description": "URLs of a GPG key files that can be used for signing metadata and packages of this repository.",
+        "minItems": 1,
+        "items": {
+          "type": "string",
+          "minLength": 1
+        }
+      },
+      "metalink": {
+        "type": "string",
+        "description": "URL of a metalink for the repository.",
+        "minLength": 1
+      },
+      "mirrorlist": {
+        "type": "string",
+        "description": "URL of a mirrorlist for the repository.",
+        "minLength": 1
+      },
+      "module_hotfixes": {
+        "type": "boolean",
+        "description": "Set this to True to disable module RPM filtering and make all RPMs from the repository available."
+      },
+      "name": {
+        "type": "string",
+        "description": "A human-readable name of the repository. Defaults to the ID of the repository.",
+        "minLength": 1
+      },
+      "priority": {
+        "type": "integer",
+        "description": "The priority value of this repository."
+      },
+      "gpgcheck": {
+        "type": "boolean",
+        "description": "Whether to perform GPG signature check on packages found in this repository."
+      },
+      "repo_gpgcheck": {
+        "type": "boolean",
+        "description": "Whether to perform GPG signature check on this repository's metadata."
+      }
+    }
+  }
+},
+"additionalProperties": false,
+"description": "YUM / DNF repo file configuration.",
+"properties": {
+  "filename": {
+    "type": "string",
+    "pattern": "^[\\w.-]{1,250}\\.repo$",
+    "description": "Repo file name."
+  },
+  "repos": {
+    "type": "array",
+    "description": "YUM / DNF repo definitions.",
+    "minItems": 1,
+    "items": {
+        "$ref": "#/definitions/repo"
+    }
+  }
+}
+"""
+
+
+# List of repo options which should be listed in this specific order if set
+# in the stage options.
+#
+# Reasoning: repo configurations as shipped by distributions or created by
+# various tools (COPR, RHSM) tend to order some options in a specific way,
+# therefore if we just iterated over the dictionary items, the order would
+# be different than how are repository configurations usually structured.
+SPECIFIC_ORDER_OPTIONS = [
+    "name",
+    "baseurl",
+    "metalink",
+    "mirrorlist",
+    "enabled",
+    "gpgcheck",
+    "repo_gpgcheck",
+    "gpgkey"
+]
+
+
+def option_value_to_str(value):
+    """
+    Convert allowed types of option values to string.
+
+    DNF allows string lists as a option value.
+    'dnf.conf' man page says:
+    "list   It is an option that could represent one or more strings separated by space or comma characters."
+    """
+    if isinstance(value, list):
+        value = " ".join(value)
+    elif isinstance(value, bool):
+        value = "1" if value else "0"
+    elif not isinstance(value, str):
+        value = str(value)
+    return value
+
+
+def main(tree, options):
+    filename = options.get("filename")
+    repos = options.get("repos")
+
+    yum_repos_dir = f"{tree}/etc/yum.repos.d"
+    os.makedirs(yum_repos_dir, exist_ok=True)
+
+    parser = configparser.ConfigParser()
+
+    for repo in repos:
+        repo_id = repo.pop("id")
+        parser.add_section(repo_id)
+        # Set some options in a specific order in which they tend to be
+        # written in repo files.
+        for option in SPECIFIC_ORDER_OPTIONS:
+            option_value = repo.pop(option, None)
+            if option_value is not None:
+                parser.set(repo_id, option, option_value_to_str(option_value))
+
+        for key, value in repo.items():
+            parser.set(repo_id, key, option_value_to_str(value))
+
+    # ensure that we won't overwrite an existing file
+    with open(f"{yum_repos_dir}/{filename}", "x") as f:
+        parser.write(f, space_around_delimiters=False)
+
+    return 0
+
+
+if __name__ == '__main__':
+    args = osbuild.api.arguments()
+    r = main(args["tree"], args["options"])
+    sys.exit(r)