prompt: kill matchflags

Python already lets one to embed RE flags directly in a regex, which
is a much nicer way to do things:

(?iLmsux)
        (One or more letters from the set "i", "L", "m", "s", "u", "x".)
        ...

matchflags was introduced in 67afecb8d6cc, and the record extension is the only
user. I've killed matchflag, and adjusted record code appropriately.

hgext/record.py

@@ -247,8 +247,8 b' def filterpatch(ui, chunks):'
         if resp_file[0] is not None:
             return resp_file[0]
         while True:
-            r = (ui.prompt(query + _(' [Ynsfdaq?] '), '[Ynsfdaq?]?$',
-                           matchflags=re.I) or 'y').lower()
+            r = (ui.prompt(query + _(' [Ynsfdaq?] '), '(?i)[Ynsfdaq?]?$')
+                 or 'y').lower()
             if r == '?':
                 c = record.__doc__.find('y - record this change')
                 for l in record.__doc__[c:].splitlines():

mercurial/ui.py

@@ -410,14 +410,18 b' class ui(object):'
             line = line[:-1]
         return line
 
-    def prompt(self, msg, pat=None, default="y", matchflags=0):
+    def prompt(self, msg, pat=None, default="y"):
+        """Prompt user with msg, read response, and ensure it matches pat
+
+        If not interactive -- the default is returned
+        """
         if not self.interactive: return default
         while True:
             try:
                 r = self._readline(msg + ' ')
                 if not r:
                     return default
-                if not pat or re.match(pat, r, matchflags):
+                if not pat or re.match(pat, r):
                     return r
                 else:
                     self.write(_("unrecognized response\n"))