Re: [BUG] git diff-tree --stdin doesn't accept two trees

[Junio C Hamano <gitster@pobox.com>]

Karl Hasselström <kha@treskal.com> writes:

> I'm trying to use diff-tree --stdin to diff several trees in one go.
> But I just get error messages when I feed it two space-separated trees
> (one commit works fine):
>
>   $ echo $(git rev-parse HEAD^{tree}) $(git rev-parse HEAD^^{tree}) | git diff-tree -p --stdin
>   error: Object 7bfd9971f77438858e412be0219ec78afb3ca46f not a commit
>
> This is at odds with the documentation:
>
>   --stdin::
>         When '--stdin' is specified, the command does not take
>         <tree-ish> arguments from the command line.  Instead, it
>         reads either one <commit> or a pair of <tree-ish>
>         separated with a single space from its standard input.
>
> I tried reading the code to figure out what's wrong, and as far as I
> can tell the code to do this is there, but seems to be protected by
> logic that aborts everything unless the whole input line is a valid
> commit. Or maybe I'm just confused ...

No, the documentation was made wrong during 1.2.0 timeperiod.

The feature of --stdin to take a commit and its parents on one line was
broken before that to support the common

	rev-list --parents $commits... -- $paths... |
        diff-tree --stdin -v -p

usage pattern by Porcelains.  For diff-tree to talk sensibly about
commits, it needs to see commits, not just trees.