Re: [PATCH v4 3/3] diff --no-index: support limiting by pathspec

From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Sep 24, 2025, 11:19 UTC
Message-ID: <35e55d20-d4aa-4b88-aa93-9192612fd1b8@gmx.de>
In-Reply-To: <a9cecd57-e683-4efd-9c79-5618000319f3@intel.com>

Hi Jacob,

On Tue, 23 Sep 2025, Jacob Keller wrote:

Show 13 quoted lines

> On 9/23/2025 7:57 AM, Johannes Schindelin wrote:
> 
> > However, this makes me wonder whether the logic itself is sound? It is
> > not immediately obvious to me why the `paths[0]` and `paths[1]` values
> > aren't matched against the pathspec yet their entirety is seemingly
> > skipped in `read_directory_contents()`?
> 
> I recall fiddling a lot to try and get this working. The idea here is
> that fixup_paths does some conversions to handle the DWIM logic where a
> "diff D F" becomes "diff D/F F". It returns true if both paths are
> directories, so we only enter this block when both paths are
> directories. (Which is required because we only support pathspec
> limiting for directory differences).

I do wonder, after seeing that `read_directory_contents()` has to (re-)construct a complete `strbuf` in every single invocation whether it would make more sense to construct two `strbuf`s in `diff_no_index()` and pass those along to `queue_diff()` _instead_ of `skip1`/`skip2`. The `queue_diff()` function would then have to extend these `strbuf`s as it already does with `buffer1`/`buffer2`.

That would avoid appending the same prefix only to remove it right away (with a not exactly cheap `memmove()`) during every `read_directory_contents()` invocation, too, in addition to allocating and releasing those `strbuf`s over and over again.

Ciao, Johannes