Re: misleading diff-hunk header

From: Junio C Hamano <gitster@pobox.com>
Date: Aug 21, 2012, 17:52 UTC
Message-ID: <7vfw7gdtfg.fsf@alter.siamese.dyndns.org>
In-Reply-To: <5033AC55.8080405@tim.thechases.com>

Tim Chase <git@tim.thechases.com> writes:

Show 19 quoted lines

> On 08/21/12 10:22, Thomas Rast wrote:
>> Tim Chase <git@tim.thechases.com> writes:
>> 
>>> diff.{type}.xfuncname seems to start searching backwards in
>>> from the beginning of the hunk, not the first differing line.
>> [...]
>>>   @@ -4,4 +4,5 @@ int call_me(int maybe)
>>>
>>>    int main()
>>>    {
>>>   +  return 0;
>>>    }
>>>
>>> misleadingly suggesting that the change occurred in the call_me()
>>> function, rather than in main()
>> 
>> I think that's intentional, and matches what 'diff -p' does.  It gives
>> you the context before the hunk.  After all, if a new function starts in
>> the leading context lines, you can see that in the usual diff data.

Correct. It is about "give the user _more_ hint/clue on the context of the hunk", in addition to what the user can see in the pre-context of the hunk, so it is pointless to hoist "int main()" there.

> ...  It just makes it hard for me to gather some stats on the
> functions that changed, and requires that I look in more than one
> place (both in the header, and in the leading context) rather than
> having a single authoritative place to grep.

The right way to answer "which functions were touched?" question is to ignore what you see on the hunk header "@@ .. @@" lines and only look at the patch text, running "git diff" with larger number of context lines as necessary.

If you have a large patch hunk that adds or removes two or more new functions, you would have to look at the patch text _anyway_ to learn about these two or more names---they cannot possibly both appear on the hunk header lines, so looking at the context hint there is pointless for the purpose for which you are using "diff" output.