rust: lower compile error on non-linux platforms to a warning As discussed on D9671#146704 this lowers the error to a warning. Differential Revision: https://phab.mercurial-scm.org/D9852

purge: move extension into core mercurial The motivation is simple: it's nicer to avoid gating basic functionality. To reduce the risk of people shooting themselves in the feet, `--confirm` is now the default, unless the extensions is loaded.. For review of the body of the purge command, use this instead of what hg/phabricator will show (the block of code is modified, not just moved): Differential Revision: https://phab.mercurial-scm.org/D9820

purge: also deal with directory with --confirm Getting the exact number is simple (you have to project the result of previous deletion to detect super-directory with only about-to-be-deleted content). So we use a vaguer message. Differential Revision: https://phab.mercurial-scm.org/D9819