match: make exactmatcher.visitchildrenset return file children as well Previously, if we had an exactmatcher like ['foo.txt', 'a/bar.txt', 'a/b/c/baz.txt'], we'd get back the following data: '.': {'a'} 'a': {'b'} 'a/b': {'c'} 'a/b/c': 'this' 'a/b/c/d': set() This was incorrect, since visitchildrenset explicitly says not to pay attention to 'foo.txt' and 'a/bar.txt' by not returning them or 'this'. Given the near impossibility of making visitchildrenset reliabbly produce only subdirectories, a previous commit has made it documented and expected that visitchildrenset can return a set containing both files and subdirectories to visit, instead of implying/requiring that visitchildrenset() return 'this' if there are files to visit. This makes the code for exactmatcher match this clarified documentation. Differential Revision: https://phab.mercurial-scm.org/D4365