Add tree-sitter based text objects

Mappings for:

* functions
* function arguments/parameters
* comments

lua/plugins/treesitter.lua

@@ -1,13 +1,19 @@
 return {
   'nvim-treesitter/nvim-treesitter',
   dependencies = {
+    'nvim-treesitter/nvim-treesitter-textobjects',
     -- TODO: Fork this and add CMake support
     'RRethy/nvim-treesitter-endwise',
   },
   build = ':TSUpdate',
   config = function()
     require('nvim-treesitter').setup()
-    local config = {
+    require('nvim-treesitter.configs').setup({
+      sync_install = false,
+      highlight = { enable = true },
+      indent = { enable = true },
+
+      -- List of languages that must be available
       ensure_installed = {
         'asm',
         'bash',
@@ -27,6 +33,7 @@ return {
         'gitattributes',
         'gitignore',
         'glsl',
+        'go',
         'gpg',
         'hlsl',
         'html',
@@ -34,6 +41,7 @@ return {
         'javascript',
         'jq',
         'json',
+        'julia',
         'llvm',
         'lua',
         'make',
@@ -57,17 +65,29 @@ return {
         'xml',
         'yaml',
       },
-      sync_install = false,
+
-      highlight = {
+      -- After opening statements insert end statements
-        enable = true,
+      endwise = { enable = true },
+
+      -- Text objects using Tree-sitter groups
+      textobjects = {
+        select = {
+          enable = true,
+          lookahead = true,
+          -- include_surrounding_whitespace = true,
+          keymaps = {
+            -- Function text objects
+            ['af'] = '@function.outer',
+            ['if'] = '@function.inner',
+            -- Parameter/argument text objects
+            ['a,'] = '@parameter.outer',
+            ['i,'] = '@parameter.inner',
+            -- Comment text objects
+            ['a/'] = '@comment.outer',
+            ['i/'] = '@comment.inner',
+          },
+        },
       },
-      indent = {
+    })
-        enable = true,
-      },
-      endwise = {
-        enable = true,
-      },
-    }
-    require('nvim-treesitter.configs').setup(config)
   end
 }