grep: fix --follow with no --diff nor --rev to not fall back to plain grep Before, "grep --follow" would only print matches in the working directory. Since --follow is the option to specify the search space, it should disable the plain (i.e. wdir) grep.

test-grep: add tests for --follow with/without --diff and/or paths This tests the behavior of cmdutil.walkchangerevs(). I'm going to rewrite cmdutil.walkchangerevs() to leverage the "log -f" logic, but the code coverage looked quite small. And the history traversal of "grep -f" goes wrong in various ways.