[PATCH v3 4/5] MyFirstContribution: reference "The cover letter" in GitGitGadget section

["Philippe Blain via GitGitGadget" <gitgitgadget@gmail.com>]

From: Philippe Blain <levraiphilippeblain@gmail.com>

The "Sending Patches via GitGitGadget" section mentions that the PR
title and description will be used as the cover letter, but does not
explain what is a cover letter or what should be included in it.

Refer readers to the new "The cover letter" section added in a previous
commit.

Signed-off-by: Philippe Blain <levraiphilippeblain@gmail.com>
---
 Documentation/MyFirstContribution.txt | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/Documentation/MyFirstContribution.txt b/Documentation/MyFirstContribution.txt
index f6ee5b8b1ae..9eb2dfec959 100644
--- a/Documentation/MyFirstContribution.txt
+++ b/Documentation/MyFirstContribution.txt
@@ -899,8 +899,12 @@ https://github.com/gitgitgadget/git and open a PR either with the "New pull
 request" button or the convenient "Compare & pull request" button that may
 appear with the name of your newly pushed branch.
 
-Review the PR's title and description, as it's used by GitGitGadget as the cover
-letter for your change. When you're happy, submit your pull request.
+Review the PR's title and description, as they're used by GitGitGadget
+respectively as the subject and body of the cover letter for your change. Refer
+to <<cover-letter,"The cover letter">> above for advice on how to title your
+submission and what content to include in the description.
+
+When you're happy, submit your pull request.
 
 [[run-ci-ggg]]
 === Running CI and Getting Ready to Send
-- 
gitgitgadget