Implement 'remove_primary_selection' as Alt-,

This allows removing search matches from the selection

Fixes #713

helix-core/src/selection.rs

@@ -360,6 +360,15 @@ impl Selection {
         self.normalize()
     }
 
+    /// Adds a new range to the selection and makes it the primary range.
+    pub fn remove(mut self, index: usize) -> Self {
+        self.ranges.remove(index);
+        if index < self.primary_index || self.primary_index == self.ranges.len() {
+            self.primary_index -= 1;
+        }
+        self
+    }
+
     /// Map selections over a set of changes. Useful for adjusting the selection position after
     /// applying changes to a document.
     pub fn map(self, changes: &ChangeSet) -> Self {

helix-term/src/commands.rs

@@ -290,6 +290,7 @@ impl Command {
         join_selections, "Join lines inside selection",
         keep_selections, "Keep selections matching regex",
         keep_primary_selection, "Keep primary selection",
+        remove_primary_selection, "Remove primary selection",
         completion, "Invoke completion popup",
         hover, "Show docs for item under cursor",
         toggle_comments, "Comment/uncomment selections",
@@ -4016,11 +4017,27 @@ fn keep_selections(cx: &mut Context) {
 
 fn keep_primary_selection(cx: &mut Context) {
     let (view, doc) = current!(cx.editor);
+    // TODO: handle count
 
     let range = doc.selection(view.id).primary();
     doc.set_selection(view.id, Selection::single(range.anchor, range.head));
 }
 
+fn remove_primary_selection(cx: &mut Context) {
+    let (view, doc) = current!(cx.editor);
+    // TODO: handle count
+
+    let selection = doc.selection(view.id);
+    if selection.len() == 1 {
+        cx.editor.set_error("no selections remaining".to_owned());
+        return;
+    }
+    let index = selection.primary_index();
+    let selection = selection.clone().remove(index);
+
+    doc.set_selection(view.id, selection);
+}
+
 fn completion(cx: &mut Context) {
     // trigger on trigger char, or if user calls it
     // (or on word char typing??)

helix-term/src/keymap.rs

@@ -499,6 +499,7 @@ impl Default for Keymaps {
             // TODO: and another method for inverse
 
             "," => keep_primary_selection,
+            "A-," => remove_primary_selection,
 
             // "q" => record_macro,
             // "Q" => replay_macro,