bug#25355: 26.0.50; Provide function to non-destructively replace buffer contents

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severity 25355 wishlist
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Philipp <p.stephani2@gmail.com> writes:

> There are many tools (e.g. auto-formatters) that take buffer contents,
> reformat them, and write the reformatted output somewhere.  However,
> there is no good way how to apply the modified output to the source
> buffer.  The naive way (erasing and re-inserting the buffer contents)
> loses point and markers.  Therefore there should be a function
> (e.g. `replace-buffer-contents') that calculates a minimal diff between
> the old and the new contents and uses editing operations (insert,
> delete, etc.) to apply the diff.  Ideally this would be done without any
> external tools (e.g. 'diff').

This is pretty similar (though not identical) to
https://debbugs.gnu.org/cgi/bugreport.cgi?bug=18.