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

>
> On Thu, Aug 03, 2023 at 01:16:02PM +0800, ZheNing Hu wrote:
> > > 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.
> >
> > The native diff command itself supports comparison with an empty file.
> >
> > #diff -u  /dev/null a
> > --- /dev/null 2023-07-25 16:47:50.270094301 +0800
> > +++ a 2023-08-03 13:14:16.980262362 +0800
> > @@ -0,0 +1 @@
> > +a
> >
> > So I believe this feature would also be useful in git.
>
> Sure, you can easily diff any file against any other, including if
> either one or both are empty. I think the main difference here is that
> /dev/null exists on your system without additional configuration and
> the empty blob does not exist in a Git repository without additional
> configuration (in this case, `git hash-object -w -t blob --stdin
> </dev/null`).
>
> TBH, I don't know if /dev/null existing by default is necessarily a
> solid argument in favor of having Git repositories come initialized with
> the empty blob by default.
>
> (To be clear, when I say "initialized", I mean that a Git repository
> would recognize the empty blob object's hash for any value of
> `the_hash_algo`, not that every repository would be prepared with a
> loose object by default.)
>