match: catch attempts to create case-insenstive exact matchers

Exact matchers are only created internally (as opposed to from user
input) based on a set of files that the caller collected before, so
they should always match the list exactly (i.e. case-sensitively).

mercurial/match.py

@@ -120,6 +120,9 b' def match(root, cwd, patterns, include=N'
     """
     normalize = _donormalize
     if icasefs:
+        if exact:
+            raise error.Abort(_("a case-insensitive exact matcher doesn't "
+                                "make sense"))
         dirstate = ctx.repo().dirstate
         dsnormalize = dirstate.normalize