Fix: the loading condition for fugitive is wrong

We should load fugitive in the following two situations:

+ When we open nvim in a Git repository
+ When we are inside nvim and change the working directory to a Git
  reposity

autoload/utils.vim

@@ -145,3 +145,17 @@ function! utils#Get_titlestr() abort
 
   return l:title_str
 endfunction
+
+" Check if we are inside a Git repo.
+function! utils#Inside_git_repo() abort
+  let res = system('git rev-parse --is-inside-work-tree')
+  if match(res, 'true') == -1
+    return v:false
+  else
+    " Manually trigger a speical user autocmd InGitRepo (to use it for
+    " lazyloading of fugitive by packer.nvim).
+    " See also https://github.com/wbthomason/packer.nvim/discussions/534.
+    doautocmd User InGitRepo
+    return v:true
+  endif
+endfunction

core/autocommands.vim

@@ -89,4 +89,9 @@ function! s:quit_current_win() abort
     quit
   endif
 endfunction
+
+augroup git_repo_check
+  autocmd!
+  autocmd VimEnter,DirChanged * call utils#Inside_git_repo() 
+augroup END
 "}

lua/plugins.lua

@@ -178,15 +178,7 @@ require('packer').startup(
     -- use 'airblade/vim-gitgutter'
 
     -- Git command inside vim
-    use {'tpope/vim-fugitive', cond =
-    function()
-      local res = vim.fn.system('git rev-parse --is-inside-work-tree')
-      if string.find(res, 'true') then
-        return true
-      else
-        return false
-      end
-    end}
+    use {'tpope/vim-fugitive', event = 'User InGitRepo'}
 
     -- Better git log display
     use {'rbong/vim-flog', require = 'tpope/vim-fugitive', cmd = {'Flog'}}