Revert: enahce: sync diff&branch component to buffer based of bufnr instead of BufEnter

functionally reverted commit 2b90200998
nvim gives first scratch buffer(when opened without a file) and the
first opened buffer bufnr 1 . That's why we can't relay completely
on bufnr being different to indicate file is different. So back to
BufEnter autocommands.

closes #38

lua/lualine/components/branch.lua

@@ -1,6 +1,9 @@
 -- Copyright (c) 2020-2021 shadmansaleh
 -- MIT license, see LICENSE for more details.
 local Branch = require('lualine.component'):new()
+local modules = require('lualine_require').lazy_require {
+  utils = 'lualine.utils.utils',
+}
 -- vars
 Branch.git_branch = ''
 Branch.git_dir = ''
@@ -20,12 +23,16 @@ Branch.new = function(self, options, child)
   end
   -- run watch head on load so branch is present when component is loaded
   Branch.find_git_dir()
+  -- update branch state of BufEnter as different Buffer may be on different repos
+  modules.utils.define_autocmd('BufEnter', "lua require'lualine.components.branch'.find_git_dir()")
   return new_branch
 end
 
 Branch.update_status = function(_, is_focused)
   if Branch.active_bufnr ~= vim.g.actual_curbuf then
-    -- Sync buffer
+    -- Workaround for https://github.com/hoob3rt/lualine.nvim/issues/286
+    -- See upstream issue https://github.com/neovim/neovim/issues/15300
+    -- Diff is out of sync re sync it.
     Branch.find_git_dir()
   end
   if not is_focused then

lua/lualine/components/diff.lua

@@ -63,6 +63,7 @@ Diff.new = function(self, options, child)
 
   if Diff.diff_checker_enabled then
     -- setup internal source
+    modules.utils.define_autocmd('BufEnter', "lua require'lualine.components.diff'.update_diff_args()")
     modules.utils.define_autocmd('BufWritePost', "lua require'lualine.components.diff'.update_git_diff()")
     Diff.update_diff_args()
   end
@@ -75,7 +76,9 @@ Diff.update_status = function(self, is_focused)
   local git_diff
   if Diff.diff_checker_enabled then
     if Diff.active_bufnr ~= vim.g.actual_curbuf then
-      -- Sync buffer
+      -- Workaround for https://github.com/hoob3rt/lualine.nvim/issues/286
+      -- See upstream issue https://github.com/neovim/neovim/issues/15300
+      -- Diff is out of sync re sync it.
       Diff.update_diff_args()
     end
     git_diff = Diff.git_diff