histedit: sniff-test for untracked file conflicts before prompting for rules This bug is as old as histedit, which is more than 10 years! I'm a little sad about the extra calculations here that we're just going to throw out, but I don't see any better way to look for untracked file conflicts and I want the bug fixed. Differential Revision: https://phab.mercurial-scm.org/D6882