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

> Felipe Contreras <felipe.contreras@gmail.com> writes:
>
>>> If the change in HEAD^ in the above example were to copy the whole A
>>> and C from a different file, then your !found_guilty logic would
>>> kick in and say all lines of A where copied from elsewhere in HEAD^,
>>> but again we would not learn the same information for C.
>>
>> We would, when it's the turn for C, which is not guilty at this point.
>
> In _this_ round of the while(1) loop, pass_blame_to_parent() gets
> the scoreboard and two origins (HEAD^ that we are looking at and
> HEAD^^ that is its parent); it does not even know what blame entry
> this request came from.
>
> It runs a single diff using diff_hunks(), and asks blame_chunk() to
> split all the blame entries in the scoreboard that suspect it is
> looking at may be guilty for.  Blame entry for A and C are both
> processed exactly the same way when HEAD^ is given to pass_blame()
> for the first time, which is when assign_blame() decided to call it
> with HEAD^ because it happened to have seen A before seeing C.  At
> that point, both A and C are processed, and the post-processing loop
> "Take responsibility for the remaining" will clean up remnants from
> both A and C.  After this round ends, the suspect for A and C are
> both set to HEAD^^.
>
> In the next round of the while(1) loop, C already forgot that its
> line movement happened in HEAD^.  Its suspect is now HEAD^^.  When
> "it's the turn for C" [*1*], you can say "These lines originate in
> that different path in HEAD^^", but it is too late to say "But the
> first time they appeared in the original file was HEAD^" (which is
> when they were moved from the different path in HEAD^^), isn't it?