Re: Don't complain about changed file when it hasn't changed

[Stefan Monnier]

>> The patch below is supposed to change Emacs such that if the file's
>> timestamp has changed, but the contents is still the same, it doesn't
>> prompt the user about a supersession-threat.
> Thanks.  Can you describe the use case(s) where this is important?

I think a common case nowadays is using Git's checkout and stash where
you might change a file temporarily and then get back to its previous
state (but with a different timestamp).

Another I've bumped into several times is when you "touch <file>" for
purposes such as forcing a re-compilation.

> Is it possible there are some use cases where this should be turned
> off (in which case we might need a user option)?

I couldn't think of any, but I'm not 100% positive that there can't be,
that's why I'm asking for objections here ;-)

>  . compare-buffer-substrings is sensitive to case-fold-search value of
>    the current buffer, while we want the comparison case-sensitive

Oh, indeed.  I missed that it doesn't work like compare-strings.  Thanks.

>  . need to bind coding-system-for-read to the encoding of the file's
>    buffer, otherwise you could get spurious false alarms, e.g. if the
>    file being checked was visited with non-default decoding (C-x RET c)

Yes, I noticed that recently (tho I'm not worried about false alarms,
but rather about silently considering that the file hasn't changed
although it has).

>  . the file's buffer could be unibyte, in which case you want
>    insert-file-contents-literally, I think

We could try to be more careful in this way, indeed.  But AFAIK the only
risk here is to flag a file as being changed when it hasn't, which is no
worse than what we currently do (i.e. a false alarm), so I'm not sure
it's worth the trouble.

>  . insert-file-contents could run out of memory, or hit some other
>    error, so I think you should catch any errors and consider the
>    check failed in that case

Sure.

> And, of course, please provide documentation for the feature.

Not sure what there is to document, actually (I do have a NEWS entry for
it, OTOH).


        Stefan