Re: [PATCH v2] rev-list: add option for --pretty=format without header

[Jeff King <peff@peff.net>]

On Sun, Jul 11, 2021 at 09:55:10PM +0000, brian m. carlson wrote:

> In general, we encourage users to use plumbing commands, like git
> rev-list, over porcelain commands, like git log, when scripting.
> However, git rev-list has one glaring problem that prevents it from
> being used in certain cases: when --pretty is used with a custom format,
> it always prints out a line containing "commit" and the object ID.  This
> makes it unsuitable for many scripting needs, and forces users to use
> git log instead.
> 
> While we can't change this behavior for backwards compatibility, we can
> add an option to suppress this behavior, so let's do so, and call it
> "--no-commit-header".  Additionally, add the corresponding positive
> option to switch it back on.
> 
> Note that this option doesn't affect the built-in formats, only custom
> formats.  This is exactly the same behavior as users already have from
> git log and is what most users will be used to.

Thanks for working on this. It has bugged me for at least a decade. :)

I do wish this had been made the default when we introduced
--pretty=format, but I agree we can't just change it now. This could be
something to keep in mind for future deprecation (or a large breaking
version). People would have to start saying --commit-header now to
future-proof themselves if they really want the current behavior. I'm OK
to leave any plans / warnings like that for future work.

The patch looks correct to me. I did have one small nit:

> diff --git a/Documentation/rev-list-options.txt b/Documentation/rev-list-options.txt
> index 5bf2a85f69..23388f36c3 100644
> --- a/Documentation/rev-list-options.txt
> +++ b/Documentation/rev-list-options.txt
> @@ -1064,6 +1064,14 @@ ifdef::git-rev-list[]
>  --header::
>  	Print the contents of the commit in raw-format; each record is
>  	separated with a NUL character.
> +
> +--no-commit-header::
> +	Suppress the header line containing "commit" and the object ID printed before
> +	the specified format.  This has no effect on the built-in formats; only custom
> +	formats are affected.

It wasn't immediately obvious to me what "custom formats" meant here. I
don't think we use that term elsewhere, nor do we seem to have a
succinct phrase for the concept. Maybe something like:

  only custom formats (i.e., `--pretty=format:`) are affected.

helps without making it too clunky?

-Peff