--- a/configmix/__init__.py	Sun Oct 29 17:13:32 2023 +0100
+++ b/configmix/__init__.py	Sun Oct 29 17:15:41 2023 +0100
@@ -57,6 +57,11 @@
     :keyword strict: enable strict parsing mode for parsers that support it
                      (e.g. to prevent duplicate keys)
     :type strict: bool
+    :keyword merge_lists: When ``None`` then lists will be overwritten
+                          by the merge process. When ``extend`` then
+                          lists will be extended instead.
+                          This parameter is passed to :func:`.merge`.
+    :type merge_lists: str or None
     :returns: the configuration
     :rtype: ~configmix.config.Configuration
 
@@ -64,22 +69,23 @@
     defaults = kwargs.get("defaults")
     extras = kwargs.get("extras")
     strict = kwargs.get("strict", False)
+    merge_lists = kwargs.get("merge_lists", None)
     if defaults is None:
         ex = Configuration()
     else:
-        ex = merge(None, Configuration(defaults))
+        ex = merge(None, Configuration(defaults), merge_lists=merge_lists)
     for f in files:
         if f.startswith(constants.DIR_PREFIX):
             for f2 in _get_configuration_files_from_dir(f[5:]):
                 nx = _load_cfg_from_file(f2, ignore_unknown=True, strict=strict)
                 if nx is not None:
-                    ex = merge(nx, ex)
+                    ex = merge(nx, ex, merge_lists=merge_lists)
         else:
             nx = _load_cfg_from_file(f, strict=strict)
             if nx is not None:
-                ex = merge(nx, ex)
+                ex = merge(nx, ex, merge_lists=merge_lists)
     if extras:
-        ex = merge(Configuration(extras), ex)
+        ex = merge(Configuration(extras), ex, merge_lists=merge_lists)
     return Configuration(ex)
 
 
@@ -91,22 +97,23 @@
     defaults = kwargs.get("defaults")
     extras = kwargs.get("extras")
     strict = kwargs.get("strict", False)
+    merge_lists = kwargs.get("merge_lists", None)
     if defaults is None:
         ex = Configuration()
     else:
-        ex = safe_merge(None, Configuration(defaults))
+        ex = safe_merge(None, Configuration(defaults), merge_lists=merge_lists)
     for f in files:
         if f.startswith(constants.DIR_PREFIX):
             for f2 in _get_configuration_files_from_dir(f[5:]):
                 nx = _load_cfg_from_file(f2, ignore_unknown=True, strict=strict)
                 if nx is not None:
-                    ex = safe_merge(nx, ex)
+                    ex = safe_merge(nx, ex, merge_lists=merge_lists)
         else:
             nx = _load_cfg_from_file(f, strict=strict)
             if nx is not None:
-                ex = safe_merge(nx, ex)
+                ex = safe_merge(nx, ex, merge_lists=merge_lists)
     if extras:
-        ex = safe_merge(Configuration(extras), ex)
+        ex = safe_merge(Configuration(extras), ex, merge_lists=merge_lists)
     return Configuration(ex)
 
 
@@ -389,7 +396,7 @@
         return result
 
 
-def merge(user, default, filter_comments=True, extend_lists=False):
+def merge(user, default, filter_comments=True, merge_lists=None):
     """Logically merge the configuration in `user` into `default`.
 
     :param ~configmix.config.Configuration user:
@@ -399,9 +406,10 @@
                 the base configuration where `user` is logically merged into
     :param bool filter_comments: flag whether to filter comment keys that
                    start with any of the items in :data:`.COMMENTS`
-    :param bool extend_lists: When ``True`` then lists will be
-                              extended instead of overwritten by the
-                              merge process
+    :param merge_lists: When ``None`` then lists will be overwritten
+                        by the merge process. When ``extend`` then
+                        lists will be extended instead.
+    :type merge_lists: str or None
     :returns: `user` with the necessary amendments from `default`.
               If `user` is ``None`` then `default` is returned.
 
@@ -438,14 +446,25 @@
                     # do not copy
                     del user[k]
                 else:
-                    user[k] = _merge(ukv, v, filter_comments, extend_lists)
+                    user[k] = _merge(ukv, v, filter_comments, merge_lists)
             else:
                 user[k] = v
+    elif merge_lists is not None:
+        if merge_lists == "extend":
+            if isinstance(user, list) and isinstance(default, list):
+                for idx, value in enumerate(default):
+                    user.insert(idx, value)
+        elif merge_lists == "prepend":
+            if isinstance(user, list) and isinstance(default, list):
+                user.extend(default)
+        else:
+            raise ValueError(
+                "unknown strategy for merge_lists: %s" % (merge_lists,))
     _filter_deletions(user)
     return user
 
 
-def _merge(user, default, filter_comments, extend_lists):
+def _merge(user, default, filter_comments, merge_lists):
     """Recursion helper for :func:`.merge`
 
     """
@@ -462,13 +481,24 @@
                     # do not copy
                     del user[k]
                 else:
-                    user[k] = _merge(ukv, v, filter_comments, extend_lists)
+                    user[k] = _merge(ukv, v, filter_comments, merge_lists)
             else:
                 user[k] = v
+    elif merge_lists is not None:
+        if merge_lists == "extend":
+            if isinstance(user, list) and isinstance(default, list):
+                for idx, value in enumerate(default):
+                    user.insert(idx, value)
+        elif merge_lists == "prepend":
+            if isinstance(user, list) and isinstance(default, list):
+                user.extend(default)
+        else:
+            raise ValueError(
+                "unknown strategy for merge_lists: %s" % (merge_lists,))
     return user
 
 
-def safe_merge(user, default, filter_comments=True, extend_lists=False):
+def safe_merge(user, default, filter_comments=True, merge_lists=None):
     """A more safe version of :func:`.merge` that makes deep copies of
     the returned container objects.
 
@@ -499,14 +529,25 @@
                     # do not copy
                     del user[k]
                 else:
-                    user[k] = _safe_merge(ukv, v, filter_comments, extend_lists)
+                    user[k] = _safe_merge(ukv, v, filter_comments, merge_lists)
             else:
                 user[k] = copy.deepcopy(v)
+    elif merge_lists is not None:
+        if merge_lists == "extend":
+            if isinstance(user, list) and isinstance(default, list):
+                for idx, value in enumerate(default):
+                    user.insert(idx, copy.deepcopy(value))
+        elif merge_lists == "prepend":
+            if isinstance(user, list) and isinstance(default, list):
+                user.extend(copy.deepcopy(default))
+        else:
+            raise ValueError(
+                "unknown strategy for merge_lists: %s" % (merge_lists,))
     _filter_deletions(user)
     return user
 
 
-def _safe_merge(user, default, filter_comments, extend_lists):
+def _safe_merge(user, default, filter_comments, merge_lists):
     """Recursion helper for :func:`safe_merge`
 
     """
@@ -523,9 +564,20 @@
                     # do not copy
                     del user[k]
                 else:
-                    user[k] = _safe_merge(ukv, v, filter_comments, extend_lists)
+                    user[k] = _safe_merge(ukv, v, filter_comments, merge_lists)
             else:
                 user[k] = copy.deepcopy(v)
+    elif merge_lists is not None:
+        if merge_lists == "extend":
+            if isinstance(user, list) and isinstance(default, list):
+                for idx, value in enumerate(default):
+                    user.insert(idx, copy.deepcopy(value))
+        elif merge_lists == "prepend":
+            if isinstance(user, list) and isinstance(default, list):
+                user.extend(copy.deepcopy(default))
+        else:
+            raise ValueError(
+                "unknown strategy for merge_lists: %s" % (merge_lists,))
     return user