Re: [RFC] [GSoC] Port git-add--interactive.perl:status_cmd to C

From: Junio C Hamano <gitster@pobox.com>
Date: May 2, 2017, 04:20 UTC
Message-ID: <xmqqvapjdh3x.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <xmqqo9vcf68f.fsf@gitster.mtv.corp.google.com>

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

Show 14 quoted lines

> "Daniel Ferreira (theiostream)" <bnmvco@gmail.com> writes:
>
>> Reproducing either of these comparisons "natively" would simply
>> require running run_diff_index() or run_diff_files() with
>> DIFF_FORMAT_NUMSTAT and tweaking diff_flush() to format appropriately
>> for the "interactive--add case".
>
> A more usual way to drive the diff machinery and react to its
> findings is to use DIFF_FORMAT_CALLBACK interface, and walk the
> collected diff_queue to work on the paths discovered.  The way
> wt-status.c builds "Changes to be committed" list out of the
> "diff-index --cached" it internally runs and "Changes not staged for
> commit" out of the "diff-files" it internally runs would be a good
> example to study.

Ahh, you'd also want to show the numstat equivalent and eventually you'd need to spool the actual textual diff in-core, so that you can present hunks to the user and have them accepted/rejected interactively. CALLBACK interface is not a good match for that task.

Of course, using a temporary file to buffer output from diff would be an obvious and simple workaround (and this is not a performance critical part of the system---we are talking about end user choosing hunks interactively after all). A cleaner may be to spawn diff-index and diff-files and read from them via pipe into core.