Improve regexp advice again, and unchain ranges

* doc/lispref/searching.texi (Regexp Special):
Mention char classes earlier, in a more-logical place.
Advise sticking to ASCII letters and digits in ranges.
Reword negative advice to make it clearer that it’s negative.
* lisp/files.el (make-auto-save-file-name):
* lisp/gnus/message.el (message-mailer-swallows-blank-line):
* lisp/gnus/nndoc.el (nndoc-lanl-gov-announce-type-p)
(nndoc-generate-lanl-gov-head):
* lisp/org/org-eshell.el (org-eshell-open):
* lisp/org/org.el (org-deadline-time-hour-regexp)
(org-scheduled-time-hour-regexp):
* lisp/progmodes/bat-mode.el (bat-font-lock-keywords):
* lisp/progmodes/bug-reference.el (bug-reference-bug-regexp):
* lisp/textmodes/less-css-mode.el (less-css-font-lock-keywords):
* lisp/vc/vc-cvs.el (vc-cvs-valid-symbolic-tag-name-p):
* lisp/vc/vc-svn.el (vc-svn-valid-symbolic-tag-name-p):
Avoid attempts to chain ranges, as this can be confusing.
For example, instead of [0-9-_.], use [0-9_.-].

1 files changed, 1 insertions, 1 deletions

diff --git a/lisp/vc/vc-svn.el b/lisp/vc/vc-svn.el
index 618f03eedc5..3c50c8fff64 100644
--- a/lisp/vc/vc-svn.el
+++ b/lisp/vc/vc-svn.el
@@ -759,7 +759,7 @@ Set file properties accordingly.  If FILENAME is non-nil, return its status."
   ;; an uppercase or lowercase letter and can contain uppercase and
   ;; lowercase letters, digits, `-', and `_'.
   (and (string-match "^[a-zA-Z]" tag)
-       (not (string-match "[^a-z0-9A-Z-_]" tag))))
+       (not (string-match "[^a-z0-9A-Z_-]" tag))))
 
 (defun vc-svn-valid-revision-number-p (tag)
   "Return non-nil if TAG is a valid revision number."