Add support for user mappings, bound to comma

:map have a 'user' mode that is accessible through the comma key.
the mapping will get executed in normal mode.

src/commands.cc

@@ -938,6 +938,7 @@ KeymapMode parse_keymap_mode(const String& str)
     if (prefix_match("prompt", str)) return KeymapMode::Prompt;
     if (prefix_match("goto", str))   return KeymapMode::Goto;
     if (prefix_match("view", str))   return KeymapMode::View;
+    if (prefix_match("user", str))   return KeymapMode::User;
 
     throw runtime_error("unknown keymap mode '" + str + "'");
 }
@@ -954,7 +955,8 @@ const CommandDesc map_key_cmd = {
     "    normal\n"
     "    insert\n"
     "    menu\n"
-    "    prompt\n",
+    "    prompt\n"
+    "    user\n",
     ParameterDesc{ SwitchMap{}, ParameterDesc::Flags::None, 4, 4 },
     CommandFlags::None,
     [](const Context& context, CompletionFlags flags,
@@ -1380,7 +1382,7 @@ private:
 
 }
 
-void exec_keys(const KeyList& keys, Context& context)
+void exec_keys(memoryview<Key> keys, Context& context)
 {
     RegisterRestorer quote('"', context);
     RegisterRestorer slash('/', context);

src/commands.hh

@@ -2,6 +2,7 @@
 #define commands_hh_INCLUDED
 
 #include "keys.hh"
+#include "memoryview.hh"
 
 namespace Kakoune
 {
@@ -9,7 +10,7 @@ namespace Kakoune
 class Context;
 
 void register_commands();
-void exec_keys(const KeyList& keys, Context& context);
+void exec_keys(memoryview<Key> keys, Context& context);
 
 }
 

src/keymap_manager.hh

@@ -19,6 +19,7 @@ enum class KeymapMode : int
     Menu,
     Goto,
     View,
+    User,
 };
 
 template<typename T> class memoryview;

src/normal.cc

@@ -1262,6 +1262,19 @@ void redo(Context& context, NormalParams)
         context.print_status({ "nothing left to redo", get_face("Information") });
 }
 
+void exec_user_mappings(Context& context, NormalParams params)
+{
+    on_next_key_with_autoinfo(context, KeymapMode::None,
+                             [params](Key key, Context& context) mutable {
+        if (not context.keymaps().is_mapped(key, KeymapMode::User))
+            return;
+
+        auto mapping = context.keymaps().get_mapping(key, KeymapMode::User);
+        ScopedEdition edition(context);
+        exec_keys(mapping, context);
+    }, "user mapping", "enter user key");
+}
+
 template<typename T>
 class Repeated
 {
@@ -1448,6 +1461,8 @@ KeyMap keymap =
     { '@', { "convert tabs to spaces in selections", tabs_to_spaces } },
     { alt('@'), { "convert spaces to tabs in selections", spaces_to_tabs } },
 
+    { ',', { "user mappings", exec_user_mappings } },
+
     { Key::Left,  { "move left", move<CharCount, Backward> } },
     { Key::Down,  { "move down", move<LineCount, Forward> } },
     { Key::Up,    { "move up", move<LineCount, Backward> } },