IncrementalInserter: support insert at line begin and append at line end

src/main.cc

@@ -512,7 +512,9 @@ std::unordered_map<char, std::function<void (Window& window, int count)>> keymap
     { 'd', do_erase },
     { 'c', do_change },
     { 'i', [](Window& window, int count) { do_insert(window, IncrementalInserter::Mode::Insert); } },
+    { 'I', [](Window& window, int count) { do_insert(window, IncrementalInserter::Mode::InsertAtLineBegin); } },
     { 'a', [](Window& window, int count) { do_insert(window, IncrementalInserter::Mode::Append); } },
+    { 'A', [](Window& window, int count) { do_insert(window, IncrementalInserter::Mode::AppendAtLineEnd); } },
     { 'o', [](Window& window, int count) { do_insert(window, IncrementalInserter::Mode::OpenLineBelow); } },
     { 'O', [](Window& window, int count) { do_insert(window, IncrementalInserter::Mode::OpenLineAbove); } },
 

src/window.cc

@@ -399,17 +399,23 @@ IncrementalInserter::IncrementalInserter(Window& window, Mode mode)
         case Mode::Change: pos = sel.begin(); break;
 
         case Mode::OpenLineBelow:
-            pos = sel.last();
+        case Mode::AppendAtLineEnd:
+            pos = sel.end() - 1;
             while (not pos.is_end() and *pos != '\n')
                 ++pos;
+            if (mode == Mode::OpenLineBelow)
+            {
                 ++pos;
                 window.m_buffer.insert(pos, "\n");
+            }
             break;
 
         case Mode::OpenLineAbove:
+        case Mode::InsertAtLineBegin:
             pos = sel.begin();
             while (not pos.is_begin() and *pos != '\n')
                 --pos;
+            if (mode == Mode::OpenLineAbove)
                 window.m_buffer.insert(pos, "\n");
             ++pos;
             break;

src/window.hh

@@ -105,6 +105,8 @@ public:
         Insert,
         Append,
         Change,
+        InsertAtLineBegin,
+        AppendAtLineEnd,
         OpenLineBelow,
         OpenLineAbove
     };