config.txt,diff-options.txt: porcelain vs. plumbing for color.diff

Reading the diff-family and config man pages one may think that the
color.diff and color.ui settings apply to all diff commands. Make it
clearer that they do not apply to the plumbing variants
diff-{files,index,tree}.

Signed-off-by: Michael J Gruber <git@drmicha.warpmail.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 11 insertions, 4 deletions

diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
index c93124b..c26e494 100644
--- a/Documentation/diff-options.txt
+++ b/Documentation/diff-options.txt
@@ -120,12 +120,19 @@ any of those replacements occurred.
 
 --color[=<when>]::
 	Show colored diff.
-	The value must be always (the default), never, or auto.
+	The value must be `always` (the default for `<when>`), `never`, or `auto`.
+	The default value is `never`.
+ifdef::git-diff[]
+	It can be changed by the `color.ui` and `color.diff`
+	configuration settings.
+endif::git-diff[]
 
 --no-color::
-	Turn off colored diff, even when the configuration file
-	gives the default to color output.
-	Same as `--color=never`.
+	Turn off colored diff.
+ifdef::git-diff[]
+	This can be used to override configuration settings.
+endif::git-diff[]
+	It is the same as `--color=never`.
 
 --word-diff[=<mode>]::
 	Show a word diff, using the <mode> to delimit changed words.