git-p4: yes/no prompts should sanitize user text

When prompting the user interactively for direction, the tests are
not forgiving of user input format.

For example, the first query asks for a yes/no response. If the user
enters the full word "yes" or "no" or enters a capital "Y" the test
will fail.

Create a new function, prompt(prompt_text) where
  * prompt_text is the text prompt for the user
  * returns a single character where valid return values are
      found by inspecting prompt_text for single characters
      surrounded by square brackets

This new function must  prompt the user for input and sanitize it by
converting the response to a lower case string, trimming leading and
trailing spaces, and checking if the first character is in the list
of choices. If it is, return the first letter.

Change the current references to raw_input() to use this new function.

Since the method requires the returned text to be one of the available
choices, remove the loop from the calling code that handles response
verification.

Thanks-to: Denton Liu <liu.denton@gmail.com>
Signed-off-by: Ben Keene <seraphire@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-p4.py

@@ -167,6 +167,21 @@ def die(msg):
         sys.stderr.write(msg + "\n")
         sys.exit(1)
 
+def prompt(prompt_text):
+    """ Prompt the user to choose one of the choices
+
+    Choices are identified in the prompt_text by square brackets around
+    a single letter option.
+    """
+    choices = set(m.group(1) for m in re.finditer(r"\[(.)\]", prompt_text))
+    while True:
+        response = raw_input(prompt_text).strip().lower()
+        if not response:
+            continue
+        response = response[0]
+        if response in choices:
+            return response
+
 def write_pipe(c, stdin):
     if verbose:
         sys.stderr.write('Writing pipe: %s\n' % str(c))
@@ -1778,12 +1793,11 @@ class P4Submit(Command, P4UserMap):
         if os.stat(template_file).st_mtime > mtime:
             return True
 
-        while True:
-            response = raw_input("Submit template unchanged. Submit anyway? [y]es, [n]o (skip this patch) ")
-            if response == 'y':
-                return True
-            if response == 'n':
-                return False
+        response = prompt("Submit template unchanged. Submit anyway? [y]es, [n]o (skip this patch) ")
+        if response == 'y':
+            return True
+        if response == 'n':
+            return False
 
     def get_diff_description(self, editedFiles, filesToAdd, symlinks):
         # diff
@@ -2345,31 +2359,22 @@ class P4Submit(Command, P4UserMap):
                           " --prepare-p4-only")
                     break
                 if i < last:
-                    quit = False
-                    while True:
-                        # prompt for what to do, or use the option/variable
-                        if self.conflict_behavior == "ask":
-                            print("What do you want to do?")
-                            response = raw_input("[s]kip this commit but apply"
-                                                 " the rest, or [q]uit? ")
-                            if not response:
-                                continue
-                        elif self.conflict_behavior == "skip":
-                            response = "s"
-                        elif self.conflict_behavior == "quit":
-                            response = "q"
-                        else:
-                            die("Unknown conflict_behavior '%s'" %
-                                self.conflict_behavior)
-
-                        if response[0] == "s":
-                            print("Skipping this commit, but applying the rest")
-                            break
-                        if response[0] == "q":
-                            print("Quitting")
-                            quit = True
-                            break
-                    if quit:
+                    # prompt for what to do, or use the option/variable
+                    if self.conflict_behavior == "ask":
+                        print("What do you want to do?")
+                        response = prompt("[s]kip this commit but apply the rest, or [q]uit? ")
+                    elif self.conflict_behavior == "skip":
+                        response = "s"
+                    elif self.conflict_behavior == "quit":
+                        response = "q"
+                    else:
+                        die("Unknown conflict_behavior '%s'" %
+                            self.conflict_behavior)
+
+                    if response == "s":
+                        print("Skipping this commit, but applying the rest")
+                    if response == "q":
+                        print("Quitting")
                         break
 
         chdir(self.oldWorkingDirectory)