Add + key to duplicate selections and <a-+> to merge overlapping ones

This is an experiment and might get reverted if overlapping selections
prove too cumbersome.

Fixes #4041

doc/pages/keys.asciidoc

@@ -286,6 +286,12 @@ Yanking (copying) and pasting use the *"* register by default (See <<registers#,
 *<a-_>*::
     merge contiguous selections together (works across lines as well)
 
+*<+>*, *<plus>*::
+    duplicate each selection (generating overlapping selections)
+
+*<a-+>*, *<a-plus>*::
+    merge overlapping selections
+
 *>*, *<gt>*::
     indent selected lines
 

src/input_handler.cc

@@ -1555,8 +1555,6 @@ private:
              kak_assert(false); // invalid for interactive insert
              break;
         }
-        if (mode != InsertMode::Append and mode != InsertMode::Replace)
-            selections.sort_and_merge_overlapping();
         selections.check_invariant();
         buffer.check_invariant();
     }

src/normal.cc

@@ -2146,6 +2146,22 @@ void merge_consecutive(Context& context, NormalParams params)
     context.selections().merge_consecutive();
 }
 
+void merge_overlapping(Context& context, NormalParams params)
+{
+    ensure_forward(context, params);
+    context.selections().merge_overlapping();
+}
+
+void duplicate_selections(Context& context, NormalParams params)
+{
+    SelectionList& sels = context.selections();
+    Vector<Selection> new_sels;
+    const int count = params.count ? params.count : 2;
+    for (const auto& sel : sels)
+        new_sels.insert(new_sels.end(), count, sel);
+    context.selections().set(std::move(new_sels), sels.main_index() * count);
+}
+
 void force_redraw(Context& context, NormalParams)
 {
     if (context.has_client())
@@ -2258,6 +2274,8 @@ static constexpr HashMap<Key, NormalCmd, MemoryDomain::Undefined, KeymapBackend>
     { {alt(';')}, {"swap selections cursor and anchor", flip_selections} },
     { {alt(':')}, {"ensure selection cursor is after anchor", ensure_forward} },
     { {alt('_')}, {"merge consecutive selections", merge_consecutive} },
+    { {'+'}, {"duplicate each selection", duplicate_selections} },
+    { {alt('+')}, {"merge overlapping selections", merge_overlapping} },
 
     { {'w'}, {"select to next word start", repeated<&select<SelectMode::Replace, select_to_next_word<Word>>>} },
     { {'e'}, {"select to next word end", repeated<select<SelectMode::Replace, select_to_next_word_end<Word>>>} },

src/selection.cc

@@ -48,7 +48,7 @@ void SelectionList::set(Vector<Selection> list, size_t main)
     m_selections = std::move(list);
     m_main = main;
     m_timestamp = m_buffer->timestamp();
-    sort_and_merge_overlapping();
+    sort();
     check_invariant();
 }
 

test/regression/0-crash-on-pipe-with-selection-access/cmd

@@ -1 +1 @@
-%<a-s>|[ $kak_selection = "bar" ] && echo "yes"<ret>
+%<a-s>|[ $kak_selection = "bar" ] && echo "yes"<ret><a-+>

test/regression/1504-assertion-on-incorrect-pipe-use/cmd

@@ -1 +1 @@
-2o<esc>|echo>&2<ret>
+2o<esc>|echo>&2<ret><a-+>