vis: disable language map for replacement character of r command

The character following the `r` command in normal mode should be
treated as regular input given in insert/replace mode, that is no
tranformation should be applied. Temporarily disable the language
map for this reason.

Close martanne#382

main.c

@@ -1630,8 +1630,10 @@ static const char *selections_trim(Vis *vis, const char *keys, const Arg *arg) {
 }
 
 static const char *replace(Vis *vis, const char *keys, const Arg *arg) {
-	if (!keys[0])
+	if (!keys[0]) {
+		vis_keymap_disable(vis);
 		return NULL;
+	}
 	const char *next = vis_keys_next(vis, keys);
 	if (!next)
 		return NULL;

vis-core.h

@@ -161,6 +161,7 @@ struct Vis {
 	Map *usercmds;                       /* user registered ":"-commands */
 	Map *options;                        /* ":set"-options */
 	Map *keymap;                         /* key translation before any bindings are matched */
+	bool keymap_disabled;                /* ignore key map for next key press, gets automatically re-enabled */
 	Buffer input_queue;                  /* holds pending input keys */
 	Buffer *keys;                        /* currently active keys buffer (either the input_queue or a macro) */
 	bool errorhandler;                   /* whether we are currently in an error handler, used to avoid recursion */

vis.c

@@ -532,6 +532,10 @@ bool vis_keymap_add(Vis *vis, const char *key, const char *mapping) {
 	return map_put(vis->keymap, key, mapping);
 }
 
+void vis_keymap_disable(Vis *vis) {
+	vis->keymap_disabled = true;
+}
+
 static void window_jumplist_add(Win *win, size_t pos) {
 	Mark mark = text_mark_set(win->file->text, pos);
 	if (mark && win->jumplist)
@@ -864,7 +868,9 @@ static const char *getkey(Vis *vis) {
 	if (!key)
 		return NULL;
 	vis_info_hide(vis);
-	if (!vis->mode->input) {
+	bool use_keymap = !vis->mode->input && !vis->keymap_disabled;
+	vis->keymap_disabled = false;
+	if (use_keymap) {
 		const char *mapped = map_get(vis->keymap, key);
 		if (mapped)
 			return mapped;

vis.h

@@ -171,6 +171,8 @@ bool vis_action_register(Vis*, const KeyAction*);
 /* add a key mapping which is applied for all modes except insert/replace
  * before any key bindings are evaluated */
 bool vis_keymap_add(Vis*, const char *key, const char *mapping);
+/* disable the keymap for the next key press */
+void vis_keymap_disable(Vis*);
 
 enum VisOperator {
 	VIS_OP_DELETE,