windows: use util.localpath for repo-relative paths in getuipathfn()

Now that we have a single place that translates from internal path
representation (slash-separated) to UI representation
(i.e. scmutil.getuipathfn()), let's switch that over to using
util.localpath for absolute paths. I don't expect any test impact on
Windows because we still respect ui.slash, which is set by the test
runner.

As Yuya pointed out, a997163e7fae (status: extract helper for
producing relative or absolute path for UI, 2019-01-29) accidentally
changed to slash-separated paths on Windows because it used used to
use repo.pathto(f, cwd='') (which calls util.localpath()) and after
that patch it just prints the filename without any
transformation. This patch should fix that regression.

Differential Revision: https://phab.mercurial-scm.org/D5935

mercurial/scmutil.py

@@ -756,8 +756,10 b' def getuipathfn(repo, legacyrelativevalu'
         cwd = repo.getcwd()
         pathto = repo.pathto
         return lambda f: pathto(f, cwd)
+    elif repo.ui.configbool('ui', 'slash'):
+        return lambda f: f
     else:
-        return lambda f: f
+        return util.localpath
 
 def subdiruipathfn(subpath, uipathfn):
     '''Create a new uipathfn that treats the file as relative to subpath.'''