Merge branch 'ei/worktree+filter'

* ei/worktree+filter:
  filter-branch: always export GIT_DIR if it is set
  setup_git_directory: fix segfault if repository is found in cwd
  test GIT_WORK_TREE
  extend rev-parse test for --is-inside-work-tree
  Use new semantics of is_bare/inside_git_dir/inside_work_tree
  introduce GIT_WORK_TREE to specify the work tree
  test git rev-parse
  rev-parse: introduce --is-bare-repository
  rev-parse: document --is-inside-git-dir

builtin-ls-files.c

@@ -470,7 +470,7 @@ int cmd_ls_files(int argc, const char **argv, const char *prefix)
 	}
 
 	if (require_work_tree &&
-			(is_bare_repository() || is_inside_git_dir()))
+			(!is_inside_work_tree() || is_inside_git_dir()))
 		die("This operation must be run in a work tree");
 
 	pathspec = get_pathspec(prefix, argv + i);