doc: Document ‘git-email-rewrite-header’.

* doc/git-email.texi (git-email-format-patch): Add paragraphs for how
‘git-email-rewrite-header’ might be useful.

Signed-off-by: Xinglu Chen <public@yoctocell.xyz>

1 files changed, 22 insertions, 0 deletions

diff --git a/doc/git-email.texi b/doc/git-email.texi
index 6d49c01..cd4ebfd 100644
--- a/doc/git-email.texi
+++ b/doc/git-email.texi
@@ -204,6 +204,28 @@ with @samp{git-email-send-email}.  By default, the generated patches will be
 deleted, if you don not like this behaviour, call
 @samp{git-email-format-patch} with a prefix argument (C-u).
 
+@findex git-email-rewrite-header
+In case you forgot to Cc someone while writing the command line options
+for @command{git format-patch}, you can use
+@code{git-email-rewrite-header} to add an Email address to Cc to all the
+messages.  If you have already put an address in the ``Cc'' field, and
+you still want to keep that address, you can invoke
+@code{git-email-rewrite-header} with a prefix argument, then the address
+to specified will be appended to the ``Cc'' field, rather than
+overwriting the old address.
+
+Another use of @code{git-email-rewrite-header} is when you are sending a
+multi-patchset series to a mailing list managed by Debbugs.  You first
+have to send a message to the mailing list address, then you have to
+wait for an ``acknowledgement'' message from Debbugs that tells you the
+bug number for the messages.  Once you know the bug number you can send
+followup messages to @email{@var{NNN}@@debbugs.gnu.org}, where @var{NNN}
+is the bug number.  See @uref{https://debbugs.gnu.org/Advanced.html, the
+Debbugs documentation} for more information.  Instead of having to
+manually switch to every buffer and add the ``To'' address, you can
+simply call @code{git-email-rewrite-header}, specify the ``To'' header,
+and then the appropriate Debbugs address.
+
 You can see all the customizable variables running @samp{M-x customize-group}
 @samp{<RET> =git-email <RET>}.