add test_cmp function for test scripts

Many scripts compare actual and expected output using
"diff -u". This is nicer than "cmp" because the output shows
how the two differ. However, not all versions of diff
understand -u, leading to unnecessary test failure.

This adds a test_cmp function to the test scripts and
switches all "diff -u" invocations to use it. The function
uses the contents of "$GIT_TEST_CMP" to compare its
arguments; the default is "diff -u".

On systems with a less-capable diff, you can do:

  GIT_TEST_CMP=cmp make test

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

1 files changed, 1 insertions, 1 deletions

diff --git a/t/t4105-apply-fuzz.sh b/t/t4105-apply-fuzz.sh
index 0e8d25f..3266e39 100755
--- a/t/t4105-apply-fuzz.sh
+++ b/t/t4105-apply-fuzz.sh
@@ -9,7 +9,7 @@ dotest () {
 	test_expect_success "$name" "
 		git checkout-index -f -q -u file &&
 		git apply $* &&
-		diff -u expect file
+		test_cmp expect file
 	"
 }