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git diff --exit-code misbehaving in 2.46.x

Subject: git diff --exit-code misbehaving in 2.46.x

## tl;dr

4 messages between Sep 25, 2024 and Sep 25, 2024.

replies: 3people: 3as markdown or json

Jan Wendland· Sep 25, 2024, 14:27 UTC · lore

Hey team,

git diff --exit-code in 2.46.x is unexpectedly returning a zero exit code for files marked as binary in .gitattributes where 2.45.x would correctly produce a non-zero exit code.

To reproduce: mkdir -p git-exit-code/dist cd git-exit-code git init echo "hi" > dist/main.js echo "dist/** binary" > .gitattributes git add --all git commit -m "Initial commit" echo "some change" >> dist/main.js git diff --exit-code echo $? # actual is 0, expected to be 1

Is this intended?

Kind regards Jan

René Scharfe· Sep 25, 2024, 15:26 UTC · re: Jan Wendland · lore

Re: git diff --exit-code misbehaving in 2.46.x

Am 25.09.24 um 16:27 schrieb Jan Wendland:

Show 19 quoted lines

> Hey team,
>
> git diff --exit-code in 2.46.x is unexpectedly returning a zero exit
> code for files marked as binary in .gitattributes where 2.45.x would
> correctly produce a non-zero exit code.
>
> To reproduce:
> mkdir -p git-exit-code/dist
> cd git-exit-code
> git init
> echo "hi" > dist/main.js
> echo "dist/** binary" > .gitattributes
> git add --all
> git commit -m "Initial commit"
> echo "some change" >> dist/main.js
> git diff --exit-code
> echo $? # actual is 0, expected to be 1
>
> Is this intended?

Thanks for the report! This is a known bug. The "next" branch contains a fix, 9a41735af6 (diff: report modified binary files as changes in builtin_diff(), 2024-09-21).

René

Junio C Hamano· Sep 25, 2024, 16:58 UTC · re: René Scharfe · lore

Re: git diff --exit-code misbehaving in 2.46.x

René Scharfe <l.s.r@web.de> writes:

Show 9 quoted lines

> Am 25.09.24 um 16:27 schrieb Jan Wendland:
>>
>> git diff --exit-code in 2.46.x is unexpectedly returning a zero exit
>> code for files marked as binary in .gitattributes where 2.45.x would
>> correctly produce a non-zero exit code.
>> ...
> Thanks for the report!  This is a known bug.  The "next" branch contains
> a fix, 9a41735af6 (diff: report modified binary files as changes in
> builtin_diff(), 2024-09-21).

I just noticed something curious.

9a41735a (diff: report modified binary files as changes in builtin_diff(), 2024-09-21) explains that since 1aaf69e6 (diff: shortcut for diff'ing two binary SHA-1 objects, 2014-08-16) added binary comparison, the code path always used a quick hash-only comparison. But the above report claims it is a behaviour change between 2.45 and 2.46.

It does seem to say things are different with 2.45 when binary changes were checked with --quiet/--exit-code from my manual testing, though.

Thanks.

René Scharfe· Sep 25, 2024, 18:06 UTC · re: Junio C Hamano · lore

Re: git diff --exit-code misbehaving in 2.46.x

Am 25.09.24 um 18:58 schrieb Junio C Hamano:

Show 24 quoted lines

> René Scharfe <l.s.r@web.de> writes:
>
>> Am 25.09.24 um 16:27 schrieb Jan Wendland:
>>>
>>> git diff --exit-code in 2.46.x is unexpectedly returning a zero exit
>>> code for files marked as binary in .gitattributes where 2.45.x would
>>> correctly produce a non-zero exit code.
>>> ...
>> Thanks for the report!  This is a known bug.  The "next" branch contains
>> a fix, 9a41735af6 (diff: report modified binary files as changes in
>> builtin_diff(), 2024-09-21).
>
> I just noticed something curious.
>
> 9a41735a (diff: report modified binary files as changes in
> builtin_diff(), 2024-09-21) explains that since 1aaf69e6 (diff:
> shortcut for diff'ing two binary SHA-1 objects, 2014-08-16) added
> binary comparison, the code path always used a quick hash-only
> comparison.  But the above report claims it is a behaviour change
> between 2.45 and 2.46.
>
> It does seem to say things are different with 2.45 when binary
> changes were checked with --quiet/--exit-code from my manual
> testing, though.

There are levels: If the flag diff_from_contents is disabled, diff just compares hashes (and other meta data). If diff_from_contents is enabled, it compares file contents as well. But not for binary files, since 1aaf69e6 (diff: shortcut for diff'ing two binary SHA-1 objects, 2014-08-16).

The shortcut exempts binary files from diff_from_contents. But it forgot to report changes for exit code calculation. So git diff with an option that turns on diff_from_contents (e.g. "git diff -b -q") has not been reporting a modified binary file since then.

d7b97b7185 (diff: let external diffs report that changes are uninteresting, 2024-06-09) enabled diff_from_contents by default, exposing the bug much more widely in 2.46.0.

René