log: fix handling of root (or empty) path provided by matcher (issue6478) Since 27d6956d386b "match: use '' instead of '.' for root directory", '.' should be translated to ''. We can't blame repo.file() about this because an empty string is invalid as a file path, but I found at least two callers (_makematcher() and revset.filelog()) would crash because of this path[0]. So let's make repo.file() accept an empty string. path[0] == b'/' wouldn't work on Python 3 anyways.

--- a/mercurial/logcmdutil.py	Thu Feb 25 15:18:00 2021 +0530
+++ b/mercurial/logcmdutil.py	Tue Feb 02 20:20:17 2021 +0900
@@ -845,7 +845,7 @@
         # slowpath; otherwise, we can turn off the slowpath
         if slowpath:
             for path in match.files():
-                if path == b'.' or path in repo.store:
+                if not path or path in repo.store:
                     break
             else:
                 slowpath = False