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

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

Felipe Contreras <felipe.contreras@gmail.com> writes:

> On Wed, May 22, 2013 at 10:23 PM, Felipe Contreras
> <felipe.contreras@gmail.com> wrote:
>> This doesn't make any sense:
>
> Ah, never mind, it's COPYING the one being modified, not EXTRACTING.

Yes.

The different levels of -C happens to correspond to the software
engineering practice from best to sloppy:

 - When you refactor to have a block of lines in a file , the
   original of that block would have come from another file (or the
   same file) you touched to remove duplication, so a single -C
   looks for an origin only from modified files (best).

 - When you start a new file, you may have to start from some
   boilerplate material that already exists in another file that is
   not (and does not have to be) changed in the commit you add that
   new file, so double -C -C looks for an origin of lines from other
   files, even unmodified ones, when looking at the lines in a new
   file (unfortunate but acceptable).

 - When you copy and paste without making any effort to refactor,
   you modify a file by adding new lines that match identically from
   another existing file, the latter of which does not change in the
   commit you do that copy and paste.  To find this, you need to
   look for an origin for any file from all the other files, and
   triple -C -C -C lets you do so (sloppy).