[context] Fix: microdnf doesn't respect --config option any more (RhB…

…ug:1866253)

One of previous commits adds support for loading the zchunk
configuration option in the context part. But it also caused
the configuration file to start reading early. Before setting the path
to the configuration file and instead, the default path was used.

This commit fix the problem.
There is a change: Zchunk option is global configuration option now
(not binded to context instance) and is readed/setted directly from
the global configuration when is needed. It is not problem for existing
code.

= changelog =
msg: Fix: microdnf does not respect --config option any more
type: bugfix
resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1866253

libdnf/dnf-context.cpp

@@ -155,7 +155,6 @@ typedef struct
     gboolean         enable_filelists;
     gboolean         keep_cache;
     gboolean         enrollment_valid;
-    gboolean         zchunk;
     gboolean         write_history;
     DnfLock         *lock;
     DnfTransaction  *transaction;
@@ -337,7 +336,6 @@ dnf_context_init(DnfContext *context)
     priv->check_disk_space = TRUE;
     priv->check_transaction = TRUE;
     priv->enable_filelists = TRUE;
-    priv->zchunk = libdnf::getGlobalMainConfig().zchunk().getValue();
     priv->write_history = TRUE;
     priv->state = dnf_state_new();
     priv->lock = dnf_lock_new();
@@ -999,7 +997,7 @@ dnf_context_get_only_trusted(DnfContext *context)
 
 /**
  * dnf_context_get_zchunk
- * @context: a #DnfContext instance.
+ * @context: a #DnfContext instance is not used. It is global option.
  *
  * Gets whether zchunk is enabled
  *
@@ -1010,8 +1008,8 @@ dnf_context_get_only_trusted(DnfContext *context)
 gboolean
 dnf_context_get_zchunk(DnfContext *context)
 {
-    DnfContextPrivate *priv = GET_PRIVATE(context);
-    return priv->zchunk;
+    auto & mainConf = libdnf::getGlobalMainConfig();
+    return mainConf.zchunk().getValue();
 }
 
 /**
@@ -1504,7 +1502,7 @@ dnf_context_set_only_trusted(DnfContext *context, gboolean only_trusted)
 
 /**
  * dnf_context_set_zchunk:
- * @context: a #DnfContext instance.
+ * @context: a #DnfContext instance is not used. It is global option.
  * @only_trusted: %TRUE use zchunk metadata if available
  *
  * Enables or disables the use of zchunk metadata if available.
@@ -1514,8 +1512,8 @@ dnf_context_set_only_trusted(DnfContext *context, gboolean only_trusted)
 void
 dnf_context_set_zchunk(DnfContext *context, gboolean zchunk)
 {
-    DnfContextPrivate *priv = GET_PRIVATE(context);
-    priv->zchunk = zchunk;
+    auto & mainConf = libdnf::getGlobalMainConfig();
+    mainConf.zchunk().set(libdnf::Option::Priority::RUNTIME, zchunk);
 }
 
 /**