Merge branch 'dg/myfirstobjectwalk-updates'

Update a more recent tutorial doc. * dg/myfirstobjectwalk-updates: MyFirstObjectWalk: add stderr to pipe processing MyFirstObjectWalk: fix description for counting omitted objects MyFirstObjectWalk: fix filtered object walk MyFirstObjectWalk: fix misspelled "builtins/" MyFirstObjectWalk: use additional arg in config_fn_t