t3701: add a test for interactive.diffFilter

This feature was added in 01143847db (add--interactive:
allow custom diff highlighting programs, 2016-02-27) but
never tested. Let's add a basic test.

Note that we only apply the filter when color is enabled,
so we have to use test_terminal. This is an open limitation
explicitly mentioned in the original commit. So take this
commit as testing the status quo, and not making a statement
on whether we'd want to enhance that in the future.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/t/t3701-add-interactive.sh b/t/t3701-add-interactive.sh
index 058698df6a4a9811b9db84fb5900472c47c61798..64fe56c3d57e78116e0b945d88a10fc98a483261 100755 (executable)
--- a/t/t3701-add-interactive.sh
+++ b/t/t3701-add-interactive.sh
@@ -392,6 +392,18 @@ test_expect_success TTY 'diffs can be colorized' '
        grep "$(printf "\\033")" output
 '
 
+test_expect_success TTY 'diffFilter filters diff' '
+       git reset --hard &&
+
+       echo content >test &&
+       test_config interactive.diffFilter "sed s/^/foo:/" &&
+       printf y | test_terminal git add -p >output 2>&1 &&
+
+       # avoid depending on the exact coloring or content of the prompts,
+       # and just make sure we saw our diff prefixed
+       grep foo:.*content output
+'
+
 test_expect_success 'patch-mode via -i prompts for files' '
        git reset --hard &&