Implement drop-in configuration folder (RhBug:1352234)

Author: Ondřej Sojka

AUTHORS

@@ -93,3 +93,4 @@ DNF CONTRIBUTORS
     Tomas Kasparek <tkasparek@redhat.com>
     Vladan Kudlac <vladankudlac@gmail.com>
     Will Woods <wwoods@redhat.com>
+    Ondřej Sojka <ondrej.sojka@gmail.com>

dnf/cli/cli.py

@@ -870,6 +870,7 @@ def configure(self, args, option_parser=None):
                 self.demands.cacheonly = True
             self.base.conf._configure_from_options(opts)
             self._read_conf_file(opts.releasever)
+            self.base.conf.read_dropin_dir()
             if 'arch' in opts:
                 self.base.conf.arch = opts.arch
             self.base.conf._adjust_conf_options()

dnf/conf/__init__.py

@@ -24,8 +24,8 @@
 places, hard to change and debug. The new structure here will replace that. Its
 goal is to:
 
-* accept configuration options from all three sources (the main config file,
-  repo config files, command line switches)
+* accept configuration options from all four sources (the main config file,
+  drop-in configuration folder, repo config files, command line switches)
 * handle all the logic of storing those and producing related values.
 * returning configuration values.
 * optionally: asserting no value is overridden once it has been applied

dnf/conf/config.py

@@ -42,6 +42,7 @@
 PRIO_REPOCONFIG = libdnf.conf.Option.Priority_REPOCONFIG
 PRIO_PLUGINDEFAULT = libdnf.conf.Option.Priority_PLUGINDEFAULT
 PRIO_PLUGINCONFIG = libdnf.conf.Option.Priority_PLUGINCONFIG
+PRIO_DROPINCONFIG = libdnf.conf.Option.Priority_DROPINCONFIG
 PRIO_COMMANDLINE = libdnf.conf.Option.Priority_COMMANDLINE
 PRIO_RUNTIME = libdnf.conf.Option.Priority_RUNTIME
 
@@ -417,6 +418,10 @@ def read(self, filename=None, priority=PRIO_DEFAULT):
         # update to where we read the file from
         self._set_value('config_file_path', filename, priority)
 
+    def read_dropin_dir(self, dirname=dnf.const.CONF_DROPIN_DIR, priority=PRIO_DROPINCONFIG):
+        for filename in sorted(os.listdir(dirname)):
+            self.read(os.path.join(dirname, filename), priority)
+
     @property
     def verbose(self):
         return self._get_value('debuglevel') >= dnf.const.VERBOSE_LEVEL

dnf/const.py.in

@@ -23,6 +23,7 @@ import distutils.sysconfig
 
 CONF_FILENAME='/etc/dnf/dnf.conf' # :api
 CONF_AUTOMATIC_FILENAME='/etc/dnf/automatic.conf'
+CONF_DROPIN_DIR='/etc/dnf/conf.d/'
 DISTROVERPKG=('system-release(releasever)', 'system-release',
               'distribution-release(releasever)', 'distribution-release',
               'redhat-release', 'suse-release')

doc/conf_ref.rst

@@ -29,6 +29,11 @@
 all \*.repo files found under ``/etc/yum.repos.d``. The latter is typically used
 for repository configuration and takes precedence over global configuration.
 
+It is also possible to drop configuration snippets into ``/etc/dnf/conf.d/``.
+These are read in alphabetical order and can override all configuration. Every
+option must be part of a section to be read correctly; therefore start every
+dropped-in configuration file with ``[main]`` or ``[repo]``.
+
 The configuration file has INI format consisting of section declaration and
 ``name=value`` options below each on separate line. There are two types of sections
 in the configuration files: main and repository. Main section defines all global