add: test use of brackets when color is disabled

add: test use of brackets when color is disabled

From 02156b81bbb2cafb19d702c55d45714fcf224048 Mon Sep 17 00:00:00 2001
From: Derrick Stolee <derrickstolee@github.com>
Date: Wed, 7 Jun 2023 09:39:01 -0400
Subject: [PATCH v2 2/2] add: test use of brackets when color is disabled

The interactive add command, 'git add -i', displays a menu of options
using full words. When color is enabled, the first letter of each word
is changed to a highlight color to signal that the first letter could be
used as a command. Without color, brackets ("[]") are used around these
first letters.

This behavior was not previously tested directly in t3701, so add a test
for it now. Since we use 'git add -i >actual <input' without
'force_color', the color system recognizes that colors are not available
on stdout and will be disabled by default.

This test would reproduce correctly with or without the fix in the
previous commit to make sure that color.ui is respected in 'git add'.

Reported-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>