Try to prevent 'repo sync' as a user name

When someone copies and pastes a setup line from a web page,
they might actually copy 'repo sync' onto the clipboard and wind
up pasting it into the "Your Name" prompt.  This means they will
initialize their client with the user name of "repo sync", creating
some rather funny looking commits later on.  For example:

  To setup your source tree:

    mkdir ~/code
    cd ~/code
    repo init -u git://....
    repo sync

If this entire block was just blindly copy and pasted into the
terminal, the shell won't read "repo sync" but "repo init" will.

By showing the user their full identity string, and asking them
to confirm it before we continue, we can give the hapless user a
chance to recover from this mistake, without unfairly harming those
who were actually named 'repo' by their parents.

Signed-off-by: Shawn O. Pearce <sop@google.com>

subcmds/init.py

@@ -148,20 +148,33 @@ to update the working directory files.
       print >>sys.stderr, 'fatal: %s' % str(e)
       sys.exit(1)
 
-  def _PromptKey(self, prompt, key, value):
+  def _Prompt(self, prompt, value):
     mp = self.manifest.manifestProject
 
     sys.stdout.write('%-10s [%s]: ' % (prompt, value))
     a = sys.stdin.readline().strip()
-    if a != '' and a != value:
-      mp.config.SetString(key, a)
+    if a == '':
+      return value
+    return a
 
   def _ConfigureUser(self):
     mp = self.manifest.manifestProject
 
-    print ''
-    self._PromptKey('Your Name', 'user.name', mp.UserName)
-    self._PromptKey('Your Email', 'user.email', mp.UserEmail)
+    while True:
+      print ''
+      name  = self._Prompt('Your Name', mp.UserName)
+      email = self._Prompt('Your Email', mp.UserEmail)
+
+      print ''
+      print 'Your identity is: %s <%s>' % (name, email)
+      sys.stdout.write('is this correct [yes/no]? ')
+      if 'yes' == sys.stdin.readline().strip():
+        break
+
+    if name != mp.UserName:
+      mp.config.SetString('user.name', name)
+    if email != mp.UserEmail:
+      mp.config.SetString('user.email', email)
 
   def _HasColorSet(self, gc):
     for n in ['ui', 'diff', 'status']: