bug#4816: change of coding system without inquiry

[Norbert Eisinger <eisinger@informatik.uni-muenchen.de>]

Stefan Monnier wrote:
> 
> Could you explain the context in which this problem showed up?
> (e.g. tell us why the coding system used matters, whether or not you've
> specified the coding-system in a "-*-coding-*-" cookie and why, etc...)

Cher Stefan,

we are a group in the computer science department of a German
university. The group consists of a full professor and an
assistant professor and 10 to 15 young scientists with research
duties or teaching duties or both. The young scientists typically
stay in the group for 3 or 4 years.

Our computer environment has for years been a SuSE distribution
of Linux with latin-1 locale. Recently it was replaced by a
Kubuntu distribution with utf-8 locale.

Over the years we have accumulated a large number of latin-1 files
that were created and edited by people who are no longer in the group
and who used whichever editors they liked. Some files may contain as
part of their text content information about the coding system:
"\usepackage[latin1]{inputenc}" in a LaTeX file,
"<?xml version='1.0' encoding='iso-8859-1'?>" in an XML file,
"<meta http-equiv='Content-Type' content='text/html; charset=iso-8859-1'>"
in an HTML file. Probably there are similar examples for other formats.
Depending on the format the files may also contain some form of
include mechanism that refers to a different file whose text
content contains such coding information.

The old files are still being used and edited. Sometimes people
have to make just minor modifications to an old file and do not
expect major consequences. However, if a minor modification
results in a change of the coding system, then the text content
of this file and possibly of included files may have to be adapted
in order to keep it consistent with the new actual coding system.
The colleagues are capable of repairing such inconsistencies, but
they may not notice them if the coding system changes silently.
This is why I am looking for a way to enforce a prompt whenever
the coding system is about to be changed.

In our situation there are not very few but very many files
encoded with something else than utf-8, and almost all of them
contain non-US-ASCII characters. Moreover, we never know by
which editors the files were created and subsequently edited.
Most of them do not contain "-*-coding-*-" cookies. Therefore
the new Emacs-23.2 behavior would probably not cover our case.

I don't know how frequent our situation is, but I guess that
it is not uncommon in university environments in countries
whose language needed one of the ISO-latin extensions of ASCII.


Thanks for your time and effort.

Norbert