Nvim: many small changes around whole project

.config/nvim/lua/core/config.lua

@@ -8,6 +8,11 @@ vim.opt.startofline = true
 vim.g.loaded_ruby_provider = 0
 vim.g.loaded_perl_provider = 0
 
+local undodir = vim.fn.expand('~/.cache/nvim/undo')
+vim.fn.mkdir(undodir, 'p')
+vim.opt.undodir = undodir
+vim.opt.undofile = true
+
 vim.opt.conceallevel = 1
 
 vim.opt.shell = '/bin/bash'