Eli Zaretskii <eliz@gnu.org> writes:

From: Elijah Gabe Pérez <eg642616@gmail.com>
Date: Wed, 19 Mar 2025 12:32:15 -0600

This user option tell whether 'eldoc' should display elisp function docstring.
If set to 'short' only display a short docstring, otherwise if set to
'full', display full docstring.
If set to nil do not show function docstring.

Where will the doc string be shown?

If in the echo-area, then what will happen when eldoc shows the info
on the mode line instead?

I've fixed it to only show in the echo-area and not to mode-line.

Also I've moved it to a function instead modifying existing ones,
similar to elisp-eldoc-var-docstring-with-value.

+(defcustom elisp-eldoc-show-function-docstring nil
+ "Show function docstring in `eldoc-mode'.
+If set to `short' only display a short docstring, otherwise if set to
+`full', display full docstring.

This should explain what is the "short docstring". Also, where the
documentation is shown.

I've added it.

To explain:
Instead display this full docstring:

Set each SYM to the value of its VAL.

The symbols SYM are variables; they are literal (not evaluated).
The values VAL are expressions; they are evaluated.
Thus, (setq x (1+ y)) sets x to the value of (1+ y).
The second VAL is not computed until after the first SYM is set, and so on;
each VAL can use the new value of variables set earlier in the setq.
The return value of the setq form is the value of the last VAL.

Only display it like this:

Set each SYM to the value of its VAL.

P.S. For the next version of the patch, please remember mentioning the
bug number in the commit log message.

Sure.