Update load condition for vim-fugitive

See https://stackoverflow.com/a/38088814/6064933 for how to check if we
are inside a Git repository.

lua/plugins.lua

@@ -178,7 +178,15 @@ require('packer').startup(
     -- use 'airblade/vim-gitgutter'
 
     -- Git command inside vim
-    use {'tpope/vim-fugitive', cmd = {'Git', 'Gwrite'}}
+    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}
 
     -- Better git log display
     use {'rbong/vim-flog', require = 'tpope/vim-fugitive', cmd = {'Flog'}}