Subject: docstring of read-only-mode doesn't seem to address most simplest case

From: 積丹尼 Dan Jacobson <[email-masked]>
Date: Sun, 14 Jan 2018 09:09:16 +0800

The following docstring
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read-only-mode is an interactive compiled Lisp function in
‘simple.el’.

It is bound to C-x C-q.

(read-only-mode &optional ARG)

Change whether the current buffer is read-only.
With prefix argument ARG, make the buffer read-only if ARG is
positive, otherwise make it writable.
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doesn't seem to address the case
where one just does
M-x read-only-mode
which indeed makes the buffer read-only.