bug#38736: 26.3; ellipsis in `*Messages*', doc of `format' etc.

[Drew Adams <drew.adams@oracle.com>]

The doc string of `format' doesn't tell you anything about control by
`print-level', `print-length', etc.  Please consider adding such info.

Consider trying to figure out, when looking at a message in
`*Messages*', why a long list value shows ellipsis ("..."), instead of
showing all the elements.  You try `C-h f message', which says nothing
about this.  The most it does is provide a bunch of details about the
formatting intermediary `format-message', imposed since Emacs 25.

Are details about %, `, and ' so important for `message' that they
merit a paragraph, but `print-level' and `print-length' are not so
important?

(What's more: the doc string for `message' goes into more detail than 
the one for `format-message', which doesn't even mention %, even
though the former tells you to refer to the latter "for  details".)

Following the `format-message' link, you still get no clue about this,
but you then follow a link for `format'.  There you still get no clue
about it, but you see that %S uses `prin1'.

Following the `prin1' link you finally find out that you can control
`message's use of ellipsis using `print-length' and `print-level'.

Users shouldn't have to go through all of that (and that even assumes
that they are able to guess that following just that thread might get 
them somewhere useful).

What's true for `message' is also true for `error', etc.  At least the
doc of `format' - and probably its often-used callers, such as `message'
- should specifically mention these "print"-controlling (really just
formatting) variables.


In GNU Emacs 26.3 (build 1, x86_64-w64-mingw32)
 of 2019-08-29
Repository revision: 96dd0196c28bc36779584e47fffcca433c9309cd
Windowing system distributor `Microsoft Corp.', version 10.0.17763
Configured using:
 `configure --without-dbus --host=x86_64-w64-mingw32
 --without-compress-install 'CFLAGS=-O2 -static -g3''