fix: Attempt to make a relative $GIT_DIR absolute

Author: zhimsel

lua/nvim-tree/explorer/watch.lua

@@ -8,8 +8,11 @@ local M = {
 }
 
 local function is_git(path)
-  -- If $GIT_DIR is set, consider its value to be equivalent to '.git'
-  if path == vim.env.GIT_DIR then
+  -- If $GIT_DIR is set, consider its value to be equivalent to '.git'.
+  -- Expand $GIT_DIR (and `path`) to a full path (see :help filename-modifiers), since
+  -- it's possible to set it to a relative path. We want to make our best
+  -- effort to expand that to a valid absolute path.
+  if vim.fn.fnamemodify(path, ":p") == vim.fn.fnamemodify(vim.env.GIT_DIR, ":p") then
     return true
   elseif vim.fn.fnamemodify(path, ":t") == ".git" then
     return true