bug#50431: revert-buffer doesn't preserve read-onlyness

[Lars Ingebrigtsen]

Glenn Morris <rgm@gnu.org> writes:

> Juri Linkov wrote:
>
>> I don't know at what moment this regression occurred,
>> but now M-x revert-buffer in a read-only file buffer
>> doesn't keep it read-only.
>
> For me, it reverts it to whatever the permission bits on the file say.
> Which is IMO the correct behaviour for revert-buffer.

Yup. 

> Perhaps you are referring to a short-lived change from
> https://debbugs.gnu.org/35166#24
> which was quickly reverted?

Making revert-buffer preserve user-initiated readedness changes isn't
trivial.  We'd need to record whether the buffer is read-only because it
was read from a read-only file (and vice versa), and then use that data
point in revert-buffer (to see whether we should respect the current
readedness state or not).

-- 
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