revset: use "canonpath()" for "filelog()" pattern without explicit kind

Before this patch, revset predicate "filelog()" uses "match.files()"
to get filename also for the pattern without explicit kind.

But in such case, only canonicalization of relative path is required,
and other initializations of "match" object including regexp
compilation are meaningless.

This patch uses "pathutil.canonpath()" directly for "filelog()"
pattern without explicit kind like "glob:", for efficiency.

This patch also does below as a part of introducing "canonpath()":

  - move location of "matchmod.match()" invocation, because "m" is no
    more used in "if not matchmod.patkind(pat)" code path

  - omit passing "default" argument to "matchmod.match()", because
    "pat" should have explicit kind of pattern in this code path

mercurial/revset.py

@@ -717,16 +717,15 b' def filelog(repo, subset, x):'
 
     # i18n: "filelog" is a keyword
     pat = getstring(x, _("filelog requires a pattern"))
-    m = matchmod.match(repo.root, repo.getcwd(), [pat], default='relpath',
-                       ctx=repo[None])
     s = set()
 
     if not matchmod.patkind(pat):
-        f = m.files()[0]
+        f = pathutil.canonpath(repo.root, repo.getcwd(), pat)
         fl = repo.file(f)
         for fr in fl:
             s.add(fl.linkrev(fr))
     else:
+        m = matchmod.match(repo.root, repo.getcwd(), [pat], ctx=repo[None])
         for f in repo[None]:
             if m(f):
                 fl = repo.file(f)

tests/test-revset.t

@@ -292,6 +292,12 b' ancestor can accept 0 or more arguments'
   $ log 'file("b*")'
   1
   4
+  $ log 'filelog("b")'
+  1
+  4
+  $ log 'filelog("../repo/b")'
+  1
+  4
   $ log 'follow()'
   0
   1