Help: Found odd git bug

Help: Found odd git bug

[Marc Branchaud]

Hi all,

A commit claims to add a line to a file.  Indeed, "git diff" shows the line
being added.

However, when I check out the commit, the file contains a *different* line,
with slightly modified contents.

What's more, "git show SHA:path/to/file" shows that the blob contains the
wrong line.

I found this using git 1.7.9, but 1.7.11.rc1 also shows the problem.

How can I narrow down what's causing this problem?

		M.

Re: Help: Found odd git bug

[Junio C Hamano]

Marc Branchaud <marcnarc@xiplink.com> writes:

> A commit claims to add a line to a file.  Indeed, "git diff" shows the line
> being added.
>
> However, when I check out the commit, the file contains a *different* line,
> with slightly modified contents.
>
> What's more, "git show SHA:path/to/file" shows that the blob contains the
> wrong line.
>
> I found this using git 1.7.9, but 1.7.11.rc1 also shows the problem.
>
> How can I narrow down what's causing this problem?

Without any information useful to diagnose, I would say it probably
is not a bug but is an operator error when either of the "git diff"
or "check out the commit" steps were done.  Even if you cannot share
the repository, at least a _complete_ command line with arguments is
needed.

For example, we can _reproduce_ your symptom description like this.

	$ echo this line was added >file
        $ git add file
        $ git commit -m 'added a line'
        
	$ echo another addition >file
        $ git diff
	 some context
        +another addition

	Ok, the "git diff" shows the line "another addition" being
	added.  Let's check:

	$ git show HEAD:file

	Huh? The output does not contain "another addition". What is
	going on?

What is going on in the above is an operator error, thinking the
"git diff" gave the change introduced by the commit, while it asked
the change to the working tree _since_ the commit.

Re: Help: Found odd git bug

[Marc Branchaud]

On 12-06-04 01:52 PM, Junio C Hamano wrote:
> Marc Branchaud <marcnarc@xiplink.com> writes:
> 
>> A commit claims to add a line to a file.  Indeed, "git diff" shows the line
>> being added.
>>
>> However, when I check out the commit, the file contains a *different* line,
>> with slightly modified contents.
>>
>> What's more, "git show SHA:path/to/file" shows that the blob contains the
>> wrong line.
>>
>> I found this using git 1.7.9, but 1.7.11.rc1 also shows the problem.
>>
>> How can I narrow down what's causing this problem?
> 
> Without any information useful to diagnose, I would say it probably
> is not a bug but is an operator error when either of the "git diff"
> or "check out the commit" steps were done.  Even if you cannot share
> the repository, at least a _complete_ command line with arguments is
> needed.

(Apply egg to face...)

Indeed, not a bug, nor a misunderstanding of git's workings.  Rather, the
offending file already had a line that the no-longer-problematic commit
should have replaced, instead of adding a nearly-identical new line later on
in the file.  So all this basically stems from not paying enough attention to
the diff's context surrounding the change.

Sorry for the false alarm, and thanks for the patient reply!

		M.