runtime(mail): add commentstring '> %s' to ftplugin

The new native commenting functionality is currently not used when
editing mail. One could reasonably expect it to change the "quote" state
of any given line in the mail (i.e. the preceding ">"), which would be
very handy and feel natural when editing mail. Especially since the
current file already uses "setlocal comments+=n:>".

Solution: Add commentstring to `> %s` to be used in files of type mail.

closes: #16669

Signed-off-by: Lucas Eekhof <[email protected]>
Signed-off-by: Christian Brabandt <[email protected]>

Author: eekhof

runtime/doc/filetype.txt

@@ -1,4 +1,4 @@
-*filetype.txt*	For Vim version 9.1.  Last change: 2024 Dec 04
+*filetype.txt*	For Vim version 9.1.  Last change: 2025 Feb 20
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -762,7 +762,7 @@ Options:
 		You can also format quoted text with |gq|.
 
 Local mappings:
-<LocalLeader>q   or   \\MailQuote
+<LocalLeader>q   or   \MailQuote
 	Quotes the text selected in Visual mode, or from the cursor position
 	to the end of the file in Normal mode.  This means "> " is inserted in
 	each line.

runtime/ftplugin/mail.vim

@@ -1,7 +1,7 @@
 " Vim filetype plugin file
 " Language:	Mail
 " Maintainer:	The Vim Project <https://github.com/vim/vim>
-" Last Change:	2023 Aug 10
+" Last Change:	2025 Feb 20
 " Former Maintainer:	Bram Moolenaar <[email protected]>
 
 " Only do this when not done yet for this buffer
@@ -10,7 +10,7 @@ if exists("b:did_ftplugin")
 endif
 let b:did_ftplugin = 1
 
-let b:undo_ftplugin = "setl modeline< tw< fo< comments<"
+let b:undo_ftplugin = "setl modeline< tw< fo< comments< commentstring<"
 
 " Don't use modelines in e-mail messages, avoid trojan horses and nasty
 " "jokes" (e.g., setting 'textwidth' to 5).
@@ -24,6 +24,9 @@ endif
 " Set 'formatoptions' to break text lines and keep the comment leader ">".
 setlocal fo+=tcql
 
+" Set commentstring to quoting sign ">" so comment shortcuts can be used to
+" edit quoted parts of mail
+setlocal commentstring=>\ %s
 " Add n:> to 'comments, in case it was removed elsewhere
 setlocal comments+=n:>