fix(pack): GIT_DIR/GIT_WORK_TREE env vars may interfere #39279

Problem:
With GIT_DIR/GIT_WORK_TREE set, the LSP on the vim.pack.update()
confirmation buffer does not show the correct git log on hover.

Solution:
Temporarily remove the git vars from the environment.

(cherry picked from commit e53e728c92)

runtime/lua/vim/pack/_lsp.lua

@@ -218,7 +218,11 @@ methods['textDocument/hover'] = function(params, callback)
     local res = { contents = { kind = vim.lsp.protocol.MarkupKind.Markdown, value = markdown } }
     callback(nil, res)
   end
-  vim.system(cmd, { cwd = path }, vim.schedule_wrap(on_exit))
+
+  -- temporarily clear GIT env vars
+  local env = vim.fn.environ() --- @type table<string,string>
+  env.GIT_DIR, env.GIT_WORK_TREE = nil, nil
+  vim.system(cmd, { cwd = path, env = env, clear_env = true }, vim.schedule_wrap(on_exit))
 end
 
 local dispatchers = {}

test/functional/plugin/pack_spec.lua

@@ -1463,6 +1463,9 @@ describe('vim.pack', function()
         -- textDocument/hover
         local confirm_winnr = api.nvim_get_current_win()
         local function assert_hover(pos, commit_msg)
+          -- Should not be affected by special environment variables
+          fn.setenv('GIT_WORK_TREE', t.paths.test_source_path)
+          fn.setenv('GIT_DIR', vim.fs.joinpath(t.paths.test_source_path, '.git'))
           api.nvim_win_set_cursor(0, pos)
           exec_lua(function()
             vim.lsp.buf.hover()
@@ -1482,6 +1485,9 @@ describe('vim.pack', function()
 
           local ref_pattern = 'Marvim <marvim@neovim%.io>\nDate:.*' .. vim.pesc(commit_msg)
           matches(ref_pattern, text)
+
+          exec_lua('vim.uv.os_unsetenv("GIT_WORK_TREE")')
+          exec_lua('vim.uv.os_unsetenv("GIT_DIR")')
         end
 
         assert_hover({ 14, 0 }, 'Commit from `main` to be removed')