Re: [PATCH] diff: "lisp" userdiff_driver

From: Junio C Hamano <gitster@pobox.com>
Date: Nov 18, 2025, 04:38 UTC
Message-ID: <xmqqldk4ez05.fsf@gitster.g>
In-Reply-To: <CAF5LJ4CMtEaJgDYRHXvCTUm9Pjpv2GAsMQN9D-DL-Ric3ADMXQ@mail.gmail.com>

"Scott L. Burson" <Scott@sympoiesis.com> writes:

> ...  The greater
> potential for false positives comes from the rule (in my proposal)
> that a left parenthesis in column 0 is taken as indicating a top-level
> definition, without even looking at the following characters.

I didn't respond to that part as I didn't know if you were serious or joking ;-).

Show 6 quoted lines

> Although Lisp dialects certainly vary, I have not seen one in which
> standard indentation practice does not indent internal expressions;
> certainly, Lisp mode in Emacs indents them.  And, I think the rule
> really does need to be that broad, because top-level forms don't
> always begin with "def"; indeed, one can put any executable expression
> at top level in a source file to perform load-time initializations.

Exactly, but the more important question is are they considered as the beginning of an important, and sematically distinct, block, just like the beginning of a function is. I am somewhat negative to the "anything not indented is a beginning of a significant group", as I do not know how well it meshes with the "(defXX is a beginning of a function", when they are used together.

> One solution would be to add an aliasing mechanism to the
> driver table.  Perhaps there would be other use cases for it.  If you
> would consider a patch along these lines, I can code it up.

It is not a particularly interesting part of the problem, simply because as the first approximation, we can just advertise "you can mark your lisp files as 'scheme'". A more interesting issue is if we can indeed come up with such a superset of patterns that can cover all Lisp variants that matter.