send-email: simplify Gmail example in the documentation

There is no need for use to manually call ‘git credential’ especially
as the interface isn’t super user-friendly and a bit confusing.  ‘git
send-email’ will do that for them at the first execution and if the
password matches, it will be saved in the store.

Simplify the documentaion so it dosn’t include the ‘git credential’
invocation (which was incorrect anyway as it should use ‘approve’
instead of ‘fill’) and instead just mentions that credentials helper
must be set up.

Signed-off-by: Michał Nazarewicz <mina86@mina86.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-send-email.txt

@@ -452,16 +452,7 @@ edit ~/.gitconfig to specify your account settings:
 
 If you have multifactor authentication setup on your gmail acocunt, you will
 need to generate an app-specific password for use with 'git send-email'. Visit
-https://security.google.com/settings/security/apppasswords to setup an
-app-specific password.  Once setup, you can store it with the credentials
-helper:
-
-	$ git credential fill
-	protocol=smtp
-	host=smtp.gmail.com
-	username=youname@gmail.com
-	password=app-password
-
+https://security.google.com/settings/security/apppasswords to create it.
 
 Once your commits are ready to be sent to the mailing list, run the
 following commands:
@@ -470,6 +461,11 @@ following commands:
 	$ edit outgoing/0000-*
 	$ git send-email outgoing/*
 
+The first time you run it, you will be prompted for your credentials.  Enter the
+app-specific or your regular password as appropriate.  If you have credential
+helper configured (see linkgit:git-credential[1]), the password will be saved in
+the credential store so you won't have to type it the next time.
+
 Note: the following perl modules are required
       Net::SMTP::SSL, MIME::Base64 and Authen::SASL