On Tue, Jul 27, 2021 at 11:29 AM Óscar Fuentes <ofv@wanadoo.es> wrote:

I think that the author was trying to preserve the user's decision about
the read-only-ness of the buffer, assuming that the file's permissions
did not change since last visit.

AFAIK currently we have no method for distinguising if the buffer was
made read-only/writable by the user or because Emacs reflected the file
system's permissions.

I have used `revert-buffer' for more than (gulp) 13 years to always update the buffer to changes in files on disk. That would revert the buffer contents to the latest file contents, read/write permissions, etc.

So this change was pretty much a breaking change for me. For context, I use the p4.el package[0] to check-in and check-out files from within Emacs. But after that change, M-x p4-edit checked out the file on the system, but still kept the buffer read-only. So I had to kill and reopen the buffer to have the read-only status update correctly.

[0]: https://github.com/gareth-rees/p4.el