bug#31035: 27.0.50; (apply ...) doesn't work with undo-in-region

[Stefan Monnier]

Package: Emacs
Version: 27.0.50


As brought up by Johan, the (apply ...) elements in buffer-undo-list are
"too powerful".  Even though BEG/END/DELTA are provided, with the
intention to make it possible for undo-in-region to handle those
entries, undo-in-region does not handle those entries.

The main problem being that undo-in-region (as well as
erc-update-undo-list, incidentally) needs not just to know which part of
the buffer is modified and with which DELTA, but it also needs to be
able to create a new entry to apply the same change at another
buffer position.


        Stefan



In GNU Emacs 27.0.50 (build 1, x86_64-unknown-linux-gnu, GTK+ Version 3.22.26)
 of 2018-03-01 built on alfajor
Repository revision: 2d65141a5654c475746bd78d998877901a0ff065
Windowing system distributor 'The X.Org Foundation', version 11.0.11906000
System Description: Debian GNU/Linux buster/sid

Recent messages:
Saving file /home/monnier/src/emacs/elpa/packages/auctex/bib-cite.el...
Wrote /home/monnier/src/emacs/elpa/packages/auctex/bib-cite.el
Mark set [4 times]
Saving file /home/monnier/src/emacs/elpa/packages/auctex/bib-cite.el...
Wrote /home/monnier/src/emacs/elpa/packages/auctex/bib-cite.el
Finding changes in 
/home/monnier/src/emacs/elpa/packages/auctex/bib-cite.el...done
Power AC, battery Charging (63.5% load, remaining time 0:53)
2.6
2.4


Configured using:
 'configure -C --enable-checking --with-modules --enable-check-lisp-object-type
 'CFLAGS=-Wall -g3 -Og -Wno-pointer-sign'
 PKG_CONFIG_PATH=/home/monnier/lib/pkgconfig'

Configured features:
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GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB TOOLKIT_SCROLL_BARS
GTK3 X11 MODULES THREADS LCMS2

Important settings:
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Major mode: InactiveMinibuffer

Minor modes in effect:
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/home/monnier/src/emacs/elpa/packages/ada-mode/ada-prj hides 
/home/monnier/src/emacs/work/lisp/progmodes/ada-prj
/home/monnier/src/emacs/elpa/packages/ada-mode/ada-xref hides 
/home/monnier/src/emacs/work/lisp/progmodes/ada-xref
/home/monnier/src/emacs/elpa/packages/hyperbole/set hides 
/home/monnier/src/emacs/work/lisp/emacs-lisp/set
/home/monnier/src/emacs/elpa/packages/landmark/landmark hides 
/home/monnier/src/emacs/work/lisp/obsolete/landmark
/home/monnier/src/emacs/elpa/packages/crisp/crisp hides 
/home/monnier/src/emacs/work/lisp/obsolete/crisp

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Memory information:
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