Bug Report: Superfluous Tab Characters

Bug Report: Superfluous Tab Characters

[Diogo Fernandes]

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Dear git team,

I have run into a bug where git seems to be adding superfluous tabs to
the end of filenames that contain a space. I have attached the output
of `git bugreport` for your review. Feel free to have a look
https://github.com/trufflesecurity/trufflehog/issues/1060 for
additional context.

Thanks.

Regards,
Diogo Fernandes

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Thank you for filling out a Git bug report!
Please answer the following questions to help us understand your issue.

What did you do before the bug happened? (Steps to reproduce your issue)

$ mkdir test
$ cd test
$ git init
$ echo foo > "filename 2"
$ git add "filename 2"
$ git commit -m "test"
$ git log -p | grep "+++" | xxd  # 0x09 is a \t character that is being added to a filename with a space

00000000: 2b2b 2b20 622f 6669 6c65 6e61 6d65 2032  +++ b/filename 2
00000010: 090a                                     ..

What did you expect to happen? (Expected behavior)

$ echo "foo" > filename2
4 git add .
$ git commit -m "test"
$ git log -p | grep "+++" | xxd

00000000: 2b2b 2b20 622f 6669 6c65 6e61 6d65 320a  +++ b/filename2.

What happened instead? (Actual behavior)

A tab character is being appended to filenames.

What's different between what you expected and what actually happened?

A tab character should not be appended to filenames.

Anything else you want to add: No.

Please review the rest of the bug report below.
You can delete any lines you don't wish to share.


[System Info]
git version:
git version 2.39.1
cpu: arm64
no commit associated with this build
sizeof-long: 8
sizeof-size_t: 8
shell-path: /bin/sh
feature: fsmonitor--daemon
uname: Darwin 21.6.0 Darwin Kernel Version 21.6.0: Mon Dec 19 20:43:09 PST 2022; root:xnu-8020.240.18~2/RELEASE_ARM64_T6000 arm64
compiler info: clang: 14.0.0 (clang-1400.0.29.202)
libc info: no libc information available
$SHELL (typically, interactive shell): /bin/zsh


[Enabled Hooks]

Re: Bug Report: Superfluous Tab Characters

[Martin Ågren]

Hi Diogo,

On Fri, 3 Feb 2023 at 13:50, Diogo Fernandes <diogoabfernandes@gmail.com> wrote:
>
> I have run into a bug where git seems to be adding superfluous tabs to
> the end of filenames that contain a space. I have attached the output
> of `git bugreport` for your review. Feel free to have a look
> https://github.com/trufflesecurity/trufflehog/issues/1060 for
> additional context.

The code that adds this tab in the output of `git log` and friends has
changed a bit since it was originally added in 1a9eb3b9d5
("git-diff/git-apply: make diff output a bit friendlier to GNU patch
(part 2)", 2006-09-22), but in that commit you can see the original
motivation.

Here's an online view:
https://github.com/git/git/commit/1a9eb3b9d50367bee8fe85022684d812816fe531

Martin

Re: Bug Report: Superfluous Tab Characters

[Martin Ågren]

On Sat, 4 Feb 2023 at 13:54, Diogo Fernandes <diogoabfernandes@gmail.com> wrote:
> On Fri, 3 Feb 2023 at 14:43 Martin Ågren <martin.agren@gmail.com> wrote:
>>
>> On Fri, 3 Feb 2023 at 13:50, Diogo Fernandes <diogoabfernandes@gmail.com> wrote:
>> >
>> > I have run into a bug where git seems to be adding superfluous tabs to
>> > the end of filenames that contain a space. I have attached the output
>> > of `git bugreport` for your review. Feel free to have a look
>> > https://github.com/trufflesecurity/trufflehog/issues/1060 for
>> > additional context.
>>
>> The code that adds this tab in the output of `git log` and friends has
>> changed a bit since it was originally added in 1a9eb3b9d5
>> ("git-diff/git-apply: make diff output a bit friendlier to GNU patch
>> (part 2)", 2006-09-22), but in that commit you can see the original
>> motivation.

> So, this is by design and not a bug? And is it still current in the latest version of git?

Yes, it appears to be by design:

    Somebody was wondering on #git channel why a git generated diff
    does not apply with GNU patch when the filename contains a SP.
    It is because GNU patch expects to find TAB (and trailing timestamp)
    on ---/+++ (old_name and new_name) lines after the filenames.

    The "diff --git" output format was carefully designed to be
    compatible with GNU patch where it can, but whitespace
    characters were always a pain.

    This adds an extra TAB (but not trailing timestamp) to old_name
    and new_name lines of git-diff output when the filename has a SP
    in it.  An earlier patch updated git-apply to prepare for this.

From a quick test, this behavior does seem to be in newest git.

I sense there is some sort of ulterior motive here that hasn't come
across yet. Are you trying to parse the output of `git log` to find
something? Would `git diff-tree` work, e.g., if you're mostly just after
the filenames involved?  Depending on what you're trying to achieve, it
could be a bit simpler to parse `git diff-tree` and other "plumbing"
commands, rather than `git log` and other such "porcelain" commands.

(Also, note that one person's `git log` output can be different from
yours, e.g., because of various config knobs being set different ways.)

Martin

Re: Bug Report: Superfluous Tab Characters

[Diogo Fernandes]

Hi Martin,

I am not personally parsing the output of git. This was rather
observed while using a third-party tool that reads the output of git
as initially pointed out by
https://github.com/trufflesecurity/trufflehog/issues/1060.

I have the latest v2.39.1 from `brew` on macOS and the tab character
is added to the output.

Anyhow, thanks for checking.

Regards,
Diogo

On Sun, Feb 5, 2023 at 4:28 PM Martin Ågren <martin.agren@gmail.com> wrote:
>
> On Sat, 4 Feb 2023 at 13:54, Diogo Fernandes <diogoabfernandes@gmail.com> wrote:
> > On Fri, 3 Feb 2023 at 14:43 Martin Ågren <martin.agren@gmail.com> wrote:
> >>
> >> On Fri, 3 Feb 2023 at 13:50, Diogo Fernandes <diogoabfernandes@gmail.com> wrote:
> >> >
> >> > I have run into a bug where git seems to be adding superfluous tabs to
> >> > the end of filenames that contain a space. I have attached the output
> >> > of `git bugreport` for your review. Feel free to have a look
> >> > https://github.com/trufflesecurity/trufflehog/issues/1060 for
> >> > additional context.
> >>
> >> The code that adds this tab in the output of `git log` and friends has
> >> changed a bit since it was originally added in 1a9eb3b9d5
> >> ("git-diff/git-apply: make diff output a bit friendlier to GNU patch
> >> (part 2)", 2006-09-22), but in that commit you can see the original
> >> motivation.
>
> > So, this is by design and not a bug? And is it still current in the latest version of git?
>
> Yes, it appears to be by design:
>
>     Somebody was wondering on #git channel why a git generated diff
>     does not apply with GNU patch when the filename contains a SP.
>     It is because GNU patch expects to find TAB (and trailing timestamp)
>     on ---/+++ (old_name and new_name) lines after the filenames.
>
>     The "diff --git" output format was carefully designed to be
>     compatible with GNU patch where it can, but whitespace
>     characters were always a pain.
>
>     This adds an extra TAB (but not trailing timestamp) to old_name
>     and new_name lines of git-diff output when the filename has a SP
>     in it.  An earlier patch updated git-apply to prepare for this.
>
> From a quick test, this behavior does seem to be in newest git.
>
> I sense there is some sort of ulterior motive here that hasn't come
> across yet. Are you trying to parse the output of `git log` to find
> something? Would `git diff-tree` work, e.g., if you're mostly just after
> the filenames involved?  Depending on what you're trying to achieve, it
> could be a bit simpler to parse `git diff-tree` and other "plumbing"
> commands, rather than `git log` and other such "porcelain" commands.
>
> (Also, note that one person's `git log` output can be different from
> yours, e.g., because of various config knobs being set different ways.)
>
> Martin