git-send-email.txt: describe --compose better

Signed-off-by: Stephen Boyd <bebarino@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-send-email.txt

@@ -60,14 +60,13 @@ The --cc option must be repeated for each user you want on the cc list.
 	Use $GIT_EDITOR, core.editor, $VISUAL, or $EDITOR to edit an
 	introductory message for the patch series.
 +
-When '--compose' is used, git send-email gets less interactive will use the
-values of the headers you set there. If the body of the email (what you type
-after the headers and a blank line) only contains blank (or GIT: prefixed)
-lines, the summary won't be sent, but git-send-email will still use the
-Headers values if you don't removed them.
+When '--compose' is used, git send-email will use the From, Subject, and
+In-Reply-To headers specified in the message. If the body of the message
+(what you type after the headers and a blank line) only contains blank
+(or GIT: prefixed) lines the summary won't be sent, but From, Subject,
+and In-Reply-To headers will be used unless they are removed.
 +
-If it wasn't able to see a header in the summary it will ask you about it
-interactively after quitting your editor.
+Missing From or In-Reply-To headers will be prompted for.
 
 --from::
 	Specify the sender of the emails.  This will default to