merge: rename conflicts to fileconflicts in _checkunknownfiles We will need to distinguish between file conflicts and path conflicts. Rename the conflicts variable so that it will be clearly distinct from pathconflicts, which will be introduced in a future commit. Differential Revision: https://phab.mercurial-scm.org/D780

merge: add _checkunknowndirs function for detecting path conflicts Add a new function which, given a file name, finds the shortest path for which there is a conflicting file or directory in the working directory. Differential Revision: https://phab.mercurial-scm.org/D779