From 4f6a803aba9e97650af304b5c266cfbc25b11fcc Mon Sep 17 00:00:00 2001
From: Tian Yuchen <cat@malon.dev>
Date: Tue, 10 Mar 2026 17:50:17 +0800
Subject: diff: document -U without <n> as using default context

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.

Hence we retain this fallback behavior for backward compatibility, but
document it as such.

Signed-off-by: Tian Yuchen <cat@malon.dev>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/diff-context-options.adoc | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

(limited to 'Documentation/diff-context-options.adoc')

diff --git a/Documentation/diff-context-options.adoc b/Documentation/diff-context-options.adoc
index e161260358..b9ace2aa4b 100644
--- a/Documentation/diff-context-options.adoc
+++ b/Documentation/diff-context-options.adoc
@@ -1,7 +1,9 @@
 `-U<n>`::
 `--unified=<n>`::
-	Generate diffs with _<n>_ lines of context. Defaults to `diff.context`
-	or 3 if the config option is unset.
+	Generate diffs with _<n>_ lines of context. The number of context
+	lines defaults to `diff.context` or 3 if the configuration variable
+	is unset. (`-U` without `<n>` is silently accepted as a synonym for
+	`-p` due to a historical accident).
 
 `--inter-hunk-context=<n>`::
 	Show the context between diff hunks, up to the specified _<number>_
-- 
cgit v1.3-5-g9baa

