Add `m` textobject for pair under cursor (#961)

helix-term/src/commands.rs

@@ -4819,6 +4819,14 @@ fn select_textobject(cx: &mut Context, objtype: textobject::TextObject) {
                         'c' => textobject_treesitter("class", range),
                         'f' => textobject_treesitter("function", range),
                         'p' => textobject_treesitter("parameter", range),
+                        'm' => {
+                            let ch = text.char(range.cursor(text));
+                            if !ch.is_ascii_alphanumeric() {
+                                textobject::textobject_surround(text, range, objtype, ch, count)
+                            } else {
+                                range
+                            }
+                        }
                         // TODO: cancel new ranges if inconsistent surround matches across lines
                         ch if !ch.is_ascii_alphanumeric() => {
                             textobject::textobject_surround(text, range, objtype, ch, count)