refactor(ui.lua): only notify the user for conceallevel in markdown f…

…iles once (#307)

lua/obsidian/ui.lua

@@ -567,20 +567,30 @@ M.setup = function(ui_opts)
     return
   end
 
-  local conceallevel = vim.opt_local.conceallevel:get()
-  if conceallevel < 1 or conceallevel > 2 then
-    log.warn(
-      "Obsidian additional syntax features require 'conceallevel' to be set to 1 or 2, "
-        .. "but you have 'conceallevel' set to '%s'.\n"
-        .. "See https://github.com/epwalsh/obsidian.nvim/issues/286 for more details.",
-      conceallevel
-    )
-  end
-
   local group = vim.api.nvim_create_augroup("obsidian_ui", { clear = true })
 
   install_hl_groups(ui_opts)
 
+  vim.api.nvim_create_autocmd({ "BufEnter" }, {
+    group = group,
+    pattern = "*.md",
+    callback = function()
+      local conceallevel = vim.opt_local.conceallevel:get()
+
+      if conceallevel < 1 or conceallevel > 2 then
+        log.warn(
+          "Obsidian additional syntax features require 'conceallevel' to be set to 1 or 2, "
+            .. "but you have 'conceallevel' set to '%s'.\n"
+            .. "See https://github.com/epwalsh/obsidian.nvim/issues/286 for more details.",
+          conceallevel
+        )
+      end
+
+      -- delete the autocommand
+      return true
+    end,
+  })
+
   vim.api.nvim_create_autocmd({ "BufEnter" }, {
     group = group,
     pattern = "*.md",