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, 3 insertions, 3 deletions

diff --git a/t/t4023-diff-rename-typechange.sh b/t/t4023-diff-rename-typechange.sh
index 255604effd..4dbfc6e8b7 100755
--- a/t/t4023-diff-rename-typechange.sh
+++ b/t/t4023-diff-rename-typechange.sh
@@ -57,7 +57,7 @@ test_expect_success 'cross renames to be detected for regular files' '
 		echo "R100	foo	bar"
 		echo "R100	bar	foo"
 	} | sort >expect &&
-	diff -u expect actual
+	test_cmp expect actual
 
 '
 
@@ -68,7 +68,7 @@ test_expect_success 'cross renames to be detected for typechange' '
 		echo "R100	foo	bar"
 		echo "R100	bar	foo"
 	} | sort >expect &&
-	diff -u expect actual
+	test_cmp expect actual
 
 '
 
@@ -79,7 +79,7 @@ test_expect_success 'moves and renames' '
 		echo "R100	foo	bar"
 		echo "T100	foo"
 	} | sort >expect &&
-	diff -u expect actual
+	test_cmp expect actual
 
 '