ZheNing Hu <adlternative@xxxxxxxxx> 于2023年7月28日周五 11:40写道： > > Taylor Blau <me@xxxxxxxxxxxx> 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@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. > > > > 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. > > Thanks, > > Taylor
