Re: [PATCH v6] Add new git-related helper to contrib

[Junio C Hamano <gitster@pobox.com>]

Junio C Hamano <gitster@pobox.com> writes:

>>> The person who moved the code will be on the list regardless,
>>
>> That is exactly the point I have been trying to raise.  Does the
>> person appear in the list when you run blame with -CCC?  You ask for
>
> s/person/commit/;
>
>> the body of the function, and the -C mode of blame sees through the
>> block-of-line movement across file boundaries, and goes straight to
>> the last commit that touched the body of the function in its original
>> file, no?

-- >8 --
cd /var/tmp/
git init blame
cd blame

cp /src/git/COPYING COPYING
git add COPYING
git commit -m initial

sed -ne 120,140p COPYING >EXTRACTING
git add EXTRACTING
git commit -m second

git blame -C -C -C EXTRACTING
-- 8< --

will show that all lines from EXTRACTING came from the original
revision of COPYING, and we will miss the line-move event.

"blame -C" with a single -C does not look at the files that did not
change in the commit that added these lines to EXTRACTING
(i.e. COPYING), so the digging stops there.

After this, if you do this:

-- >8 --
echo >>COPYING
git commit --amend -a --no-edit

git blame -C EXTRACTING
-- 8< --

then the commit that did add these lines to EXTRACTING touched
COPYING, and the origin of these lines are traced to it (this is
designed to be useful in a typical "refactor by moving code";
"cut and paste without changing the original" people need heavier
copy detection with more -C).

IIRC, git-gui runs two blames, one without any -C and one with (I do
not offhand recall how many -C it uses) to show both.

HTH.