On Wed, Jul 26, 2023 at 11:23:52AM -0700, Junio C Hamano wrote: > ZheNing Hu <adlternative@xxxxxxxxx> 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. Thanks, Taylor
