diff --git a/mercurial/scmutil.py b/mercurial/scmutil.py
--- a/mercurial/scmutil.py
+++ b/mercurial/scmutil.py
@@ -17,19 +17,37 @@ def checkfilename(f):
 def checkportable(ui, f):
     '''Check if filename f is portable and warn or abort depending on config'''
     checkfilename(f)
-    val = ui.config('ui', 'portablefilenames', 'warn')
-    lval = val.lower()
-    abort = os.name == 'nt' or lval == 'abort'
-    bval = util.parsebool(val)
-    if abort or lval == 'warn' or bval:
+    if showportabilityalert(ui):
         msg = util.checkwinfilename(f)
         if msg:
-            if abort:
-                raise util.Abort("%s: %r" % (msg, f))
-            ui.warn(_("warning: %s: %r\n") % (msg, f))
-    elif bval is None and lval != 'ignore':
+            portabilityalert(ui, "%s: %r" % (msg, f))
+
+def checkportabilityalert(ui):
+    '''check if the user's config requests nothing, a warning, or abort for
+    non-portable filenames'''
+    val = ui.config('ui', 'portablefilenames', 'warn')
+    lval = val.lower()
+    bval = util.parsebool(val)
+    abort = os.name == 'nt' or lval == 'abort'
+    warn = bval or lval == 'warn'
+    if bval is None and not (warn or abort or lval == 'ignore'):
         raise error.ConfigError(
             _("ui.portablefilenames value is invalid ('%s')") % val)
+    return abort, warn
+
+def showportabilityalert(ui):
+    '''check if the user wants any notification of portability problems'''
+    abort, warn = checkportabilityalert(ui)
+    return abort or warn
+
+def portabilityalert(ui, msg):
+    if not msg:
+        return
+    abort, warn = checkportabilityalert(ui)
+    if abort:
+        raise util.Abort("%s" % msg)
+    elif warn:
+        ui.warn(_("warning: %s\n") % msg)
 
 class path_auditor(object):
     '''ensure that a filesystem path contains no banned components.