Add command to extend selection to line above (#2117)

* added command to extend selection to line above

* fixed view not scrolling up when reaching top of the screen

* refactored shared code into separate impl

helix-term/src/commands.rs

@@ -247,6 +247,7 @@ impl MappableCommand {
         search_selection, "Use current selection as search pattern",
         global_search, "Global Search in workspace folder",
         extend_line, "Select current line, if already selected, extend to next line",
+        extend_line_above, "Select current line, if already selected, extend to previous line",
         extend_to_line_bounds, "Extend selection to line bounds (line-wise selection)",
         delete_selection, "Delete selection",
         delete_selection_noyank, "Delete selection, without yanking",
@@ -1854,7 +1855,20 @@ fn global_search(cx: &mut Context) {
     cx.jobs.callback(show_picker);
 }
 
+enum Extend {
+    Above,
+    Below,
+}
+
 fn extend_line(cx: &mut Context) {
+    extend_line_impl(cx, Extend::Below);
+}
+
+fn extend_line_above(cx: &mut Context) {
+    extend_line_impl(cx, Extend::Above);
+}
+
+fn extend_line_impl(cx: &mut Context, extend: Extend) {
     let count = cx.count();
     let (view, doc) = current!(cx.editor);
 
@@ -1863,13 +1877,22 @@ fn extend_line(cx: &mut Context) {
         let (start_line, end_line) = range.line_range(text.slice(..));
 
         let start = text.line_to_char(start_line);
-        let mut end = text.line_to_char((end_line + count).min(text.len_lines()));
+        let end = text.line_to_char((end_line + count).min(text.len_lines()));
 
-        // go to next line if current line is selected
-        if range.from() == start && range.to() == end {
-            end = text.line_to_char((end_line + count + 1).min(text.len_lines()));
-        }
-        Range::new(start, end)
+        // extend to previous/next line if current line is selected
+        let (anchor, head) = if range.from() == start && range.to() == end {
+            match extend {
+                Extend::Above => (end, text.line_to_char(start_line.saturating_sub(1))),
+                Extend::Below => (
+                    start,
+                    text.line_to_char((end_line + count + 1).min(text.len_lines())),
+                ),
+            }
+        } else {
+            (start, end)
+        };
+
+        Range::new(anchor, head)
     });
 
     doc.set_selection(view.id, selection);