grep: search working directory files by default if --all-files is specified The default was -rtip:0 before, but "--all-files -rtip:0" would be the most useless combination, and it isn't supported yet. Let's change the default to something useful. This isn't flagged as BC since --all-files isn't released. Differential Revision: https://phab.mercurial-scm.org/D3917