Re: git diff: add option for omitting the contents of deletes

> > That aspect is similar to -M and -C, though - unless we check the sha1
> > of the blobs before applying the patch (which would be possible for -D
> > also) - do we?
> 
> Yes, I think we do check the sha1s for a "-M" patch. And we should do so
> for a "-D" patch, too. Which would make it just as likely to conflict as
> a version with the actual patch content, _except_ that it relies on the
> recipient having that sha1.
> 
> I don't see how "-D" is any less reversible than -M or -C, though. If I
> get your -D patch, I use the index line to see that the blob went from
> 1234abcd to 0000000, check that we are at 1234abcd, and then delete the
> file. To reverse it, I reinstate 1234abcd from nothing (and conflict if
> the file exists). _Neither_ case works without the sha1.
> 
> So I think the problem is not about "this cannot be reversed" but about
> "the recipient must have your sha1 to make sense of it, in either
> direction". Which is the same case as with "-M" and "-C", and why we
> have long cautioned about their use on mailing lists. But the right rule
> is not "do not use on mailing lists" but rather "do not use on mailing
> lists for projects where the recipients will not be using git to apply".