Add command to merge non-consecutive ranges (#7053)

* Add command for merging non-consecutive ranges

* Add `merge_selections` command to book

* Simplify `merge_ranges`

Heeded the advice of @the-mikedavis to stop iterating over all ranges and simply merge the first and the last range, as the invariants of `Selection` guarantee that the list of ranges is always sorted and never empty.

* Clarify doc comment of `merge_ranges`

1 files changed, 8 insertions, 1 deletions

diff --git a/helix-core/src/selection.rs b/helix-core/src/selection.rs
index 259b131a..9e366c33 100644
--- a/helix-core/src/selection.rs
+++ b/helix-core/src/selection.rs
@@ -522,7 +522,14 @@ impl Selection {
         self
     }
 
-    // Merges all ranges that are consecutive
+    /// Replaces ranges with one spanning from first to last range.
+    pub fn merge_ranges(self) -> Self {
+        let first = self.ranges.first().unwrap();
+        let last = self.ranges.last().unwrap();
+        Selection::new(smallvec![first.merge(*last)], 0)
+    }
+
+    /// Merges all ranges that are consecutive.
     pub fn merge_consecutive_ranges(mut self) -> Self {
         let mut primary = self.ranges[self.primary_index];