Subject: Re: [PATCH v1] diff: document -U without <n> as using default context

From: Jean-Noël AVILA <[email-masked]>
Date: Tue, 10 Mar 2026 18:31:14 +0100

On Monday, 9 March 2026 18:27:19 CET Tian Yuchen wrote:
> The documentation for '-U<n>' implies that the numeric value '<n>' is
> mandatory. However, the command line parser has historically accepted
> '-U' without a number.
> 
> Strictly requiring a number for '-U' would break existing tests
> (e.g., in 't4013') and likely disrupt user scripts relying on this
> undocumented behavior.
> 
> Since we are retaining this fallback behavior for backward compatibility,
> update the documentation to explicitly state that '<n>' can be omitted
> for the short option '-U'.

In this case, isn't the long option also changed to optional number, such as:

`--unified[=<n>]`

?

> 
> Signed-off-by: Tian Yuchen <[email-masked]>
> ---
>  Documentation/diff-context-options.adoc | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/Documentation/diff-context-options.adoc
> b/Documentation/diff-context-options.adoc index e161260358..655496ec3a 
100644
> --- a/Documentation/diff-context-options.adoc
> +++ b/Documentation/diff-context-options.adoc
> @@ -1,4 +1,4 @@
> -`-U<n>`::
> +`-U[<n>]`::
>  `--unified=<n>`::
>  	Generate diffs with _<n>_ lines of context. Defaults to 
`diff.context`
>  	or 3 if the config option is unset.