From: Philip Oakley <philipoakley@iee.org>
Date: Wed, 01 Nov 2017 00:27:12 GMT
Subject: Re: Meaning of two commit-ish hash in git diff
Message-ID: <2A1B66E868594FC984FED8F0EDEAF900@PhilipOakley>
In-Reply-To: <xmqqd1542b5r.fsf@gitster.mtv.corp.google.com>

Yubin ,

From: "Junio C Hamano" <gitster@pobox.com>
> Yubin Ruan <ablacktshirt@gmail.com> writes:
>
>> diff --git a/path/somefile b/path/somefile
>> index f8886b4..a1c96df 100644
>> --- a/path/somefile
>> +++ b/path/somefile
>> <snip>
>>
>> This is output by a `git diff` between two adjacent commits but they are
>> not any commit hash. I grep through the whole $(git log) but still cannot
>> find those hash.
>
> The f8886b4 you see on the left is the name of the blob object on
> the left hand side of the comparison that produced this output;
> similarly a1c96df is the name of the blob object on the right hand
> side of the comparison.
>
> IOW, if you have the contents of the blob whose object name is
> f8886b4, by applying this patch, you will get a blob whose object
> name is a1c96df.
>
> The information is used by "git am -3" when the patch does not apply
> cleanly to fall back to the 3-way merge.

The ability to 'git describe` those blob object IDs is currently the subject 
of a patch series
https://public-inbox.org/git/20171031211852.13001-1-sbeller@google.com/

Maybe see if would have helped ;-)

Philip