Re: [QUESTION] how to diff one blob with nothing

>
> Taylor Blau <me@ttaylorr.com> 于2023年7月28日周五 01:46写道：
> >
> > On Wed, Jul 26, 2023 at 11:23:52AM -0700, Junio C Hamano wrote:
> > > ZheNing Hu <adlternative@gmail.com> writes:
> > >
> > > >> If you haven't created one, of course it would fail.  It should help
> > > >> to do
> > > >>
> > > >>     $ git hash-object -w --stdin </dev/null
> > > >>
> > > >> before running
> > > >>
> > > >>     $ git diff 00750edc e69de29bb
> > > >>
> > > >
> > > > This is a viable solution, but it's a bit ugly since a read-only "diff"
> > > > requires ”write“ an empty blob.
> > >
> > > If you do not even have an empty blob, you have no business
> > > comparing some other blobs you have with it, do you?
> > >
> > > If you do not have a file with a single line "hello, world\n" (that
> > > hashes to 4b5fa63702dd96796042e92787f464e28f09f17d if written in a
> > > blob), then you cannot do "git diff 4b5fa637" with anything and
> > > expect it to work.  It is the same thing.
> > >
> > > Besides, if you _know_ you want to compare a blob X to emptyness,
> > > you are better of doing "git cat-file blob X" in the first place.
> >
> > Yeah, exactly. In 346245a1bb6 (hard-code the empty tree object,
> > 2008-02-13), the rationale was partly that having the empty tree object
> > is useful for showing some diffs, such as for the initial commit.
> >
> > But I can't think of a similar argument for the empty blob. Like Junio
> > said, if you're purposefully diff-ing against the empty blob, wouldn't
> > you simply want the entire contents anyway? If that's the case, cat-file
> > seems like a much more appropriate tool.
> >
>
> Here, it is necessary to compare multiple versions of blobs while also
> considering the situations of creation and deletion.
>
> Well, what I need is the "diff" content, with lines in the diff indicating
> '+' or '-' signs. This can be achieved by manually adding them, but it is
> not very compatible with the original logic.
>