Scintilla

Committed a change that should prevent a buffer from being saved to the
same file as another buffer.

This works differently on Windows so the patch only works for GTK+. If I
get time, I'll look into making it work on Windows.

Sorry, forgot to tell that I wrote the patch on the source code of SciTE
1.76

You can find a patch attached to this comment.
A few notes about the patch:

1) while there where multiple choices ([a] closing the current buffer
and switching to the one that already have the chosen filename, [b]
preventing the action at all, [c] alerting the user and letting him
continue if he wants, etc.) with different flavors (with or without alert
to the user, configurable or not behavior, etc.), I choose a very simple
solution: preventing the save as with same filename of another buffer at
all;

2) I don't have a an adeguate development environment in my PC for
compiling and, thus, testing the patch: the patch has not been compiled nor
tested;

3) you are right about "a rarely occurring problem", so if you don't
want to lose time with this patch and/or you don't include it in SciTE,
I'll understand it.

File Added: scintilla-Bugs-1970403.patch

Disallowing saving to the same file as a current buffer would be my
preference too but its extra work for a rarely occurring problem. I'll
accept a patch.

I understand the design choice of SciTE (and I agree too: the test case
came from a real world situation in which I, by mistake, performed a "save
as" on two different buffers to the same file).

Anyway, the problem that I had with this "bug" was not that I had two
buffers for the same file and it wasn't handled correctly but, instead,
that I, by mistake, had the same file opened in two different buffers and
SciTE didn't prevent me to do it, instead it allowed me to do it and, then,
it didn't work properly with those two buffers.

Isn't it possible to explicitly disallow that a file is opened in two
different buffers using the "save as" command (at least for those cases in
which it's trivial to determine that two pathnames refers to the same
file)? Or maybe this would disallow other useful scenarios?

SciTE wasn't designed to allow having the same file opened multiple times.
While it would be slightly better to stay on the same buffer, I don't want
to support multiple buffers on the same file.