emacs-28 e3c3c78: * lisp/custom.el (defgroup): Document the :prefix keyword.

[Stefan Kangas]

branch: emacs-28
commit e3c3c78365c6430b0e9015c1a3701518de4680cd
Author: Stefan Kangas <stefan@marxist.se>
Commit: Stefan Kangas <stefan@marxist.se>

    * lisp/custom.el (defgroup): Document the :prefix keyword.
---
 lisp/custom.el | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/lisp/custom.el b/lisp/custom.el
index 858b158..cc81740 100644
--- a/lisp/custom.el
+++ b/lisp/custom.el
@@ -507,7 +507,11 @@ The remaining arguments should have the form
    [KEYWORD VALUE]...
 
 For a list of valid keywords, see the common keywords listed in
-`defcustom'.
+`defcustom'.  The keyword :prefix can only be used for
+customization groups, and means that the given string should be
+removed from variable names before creating unlispified names,
+when the user option `custom-unlispify-remove-prefixes' is
+non-nil.
 
 See Info node `(elisp) Customization' in the Emacs Lisp manual
 for more information."