MyFirstContribution: rephrase contact info

Make an effort not to discourage new users from mailing questions to
git@vger.kernel.org, and explain the purpose of the mentoring list in
contrast to the main list.

Signed-off-by: Emily Shaffer <emilyshaffer@google.com>
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/MyFirstContribution.txt

@@ -28,11 +28,24 @@ useful additional context:
 
 If you get stuck, you can seek help in the following places.
 
+==== git@vger.kernel.org
+
+This is the main Git project mailing list where code reviews, version
+announcements, design discussions, and more take place. Those interested in
+contributing are welcome to post questions here. The Git list requires
+plain-text-only emails and prefers inline and bottom-posting when replying to
+mail; you will be CC'd in all replies to you. Optionally, you can subscribe to
+the list by sending an email to majordomo@vger.kernel.org with "subscribe git"
+in the body. The https://lore.kernel.org/git[archive] of this mailing list is
+available to view in a browser.
+
 ==== https://groups.google.com/forum/#!forum/git-mentoring[git-mentoring@googlegroups.com]
 
-This mailing list is targeted to new contributors and is a great place to post
-questions and receive kind, detailed answers from volunteers on the Git
-project. You must join the group to view messages or post.
+This mailing list is targeted to new contributors and was created as a place to
+post questions and receive answers outside of the public eye of the main list.
+Veteran contributors who are especially interested in helping mentor newcomers
+are present on the list. In order to avoid search indexers, group membership is
+required to view messages; anyone can join and no approval is required.
 
 ==== https://webchat.freenode.net/#git-devel[#git-devel] on Freenode
 
@@ -46,16 +59,6 @@ respond to you. It's better to ask your questions in the channel so that you
 can be answered if you disconnect and so that others can learn from the
 conversation.
 
-==== git@vger.kernel.org
-
-This is the main Git project mailing list where code reviews, version
-announcements, design discussions, and more take place. The Git list
-requires plain-text-only emails and prefers inline and bottom-posting when
-replying to mail; you will be CC'd in all replies to you. Optionally, you can
-subscribe to the list by sending an email to majordomo@vger.kernel.org with
-"subscribe git" in the body. The https://lore.kernel.org/git[archive] of this
-mailing list is available to view in a browser.
-
 [[getting-started]]
 == Getting Started