t5304: use helper to report failure of "test foo = bar"

For small outputs, we sometimes use:

  test "$(some_cmd)" = "something we expect"

instead of a full test_cmp. The downside of this is that
when it fails, there is no output at all from the script.
Let's introduce a small helper to make tests easier to
debug.

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

t/t5304-prune.sh

@@ -13,7 +13,7 @@ add_blob() {
 	before=$(git count-objects | sed "s/ .*//") &&
 	BLOB=$(echo aleph_0 | git hash-object -w --stdin) &&
 	BLOB_FILE=.git/objects/$(echo $BLOB | sed "s/^../&\//") &&
-	test $((1 + $before)) = $(git count-objects | sed "s/ .*//") &&
+	verbose test $((1 + $before)) = $(git count-objects | sed "s/ .*//") &&
 	test_path_is_file $BLOB_FILE &&
 	test-chmtime =+0 $BLOB_FILE
 }
@@ -45,11 +45,11 @@ test_expect_success 'prune --expire' '
 
 	add_blob &&
 	git prune --expire=1.hour.ago &&
-	test $((1 + $before)) = $(git count-objects | sed "s/ .*//") &&
+	verbose test $((1 + $before)) = $(git count-objects | sed "s/ .*//") &&
 	test_path_is_file $BLOB_FILE &&
 	test-chmtime =-86500 $BLOB_FILE &&
 	git prune --expire 1.day &&
-	test $before = $(git count-objects | sed "s/ .*//") &&
+	verbose test $before = $(git count-objects | sed "s/ .*//") &&
 	test_path_is_missing $BLOB_FILE
 
 '
@@ -59,11 +59,11 @@ test_expect_success 'gc: implicit prune --expire' '
 	add_blob &&
 	test-chmtime =-$((2*$week-30)) $BLOB_FILE &&
 	git gc &&
-	test $((1 + $before)) = $(git count-objects | sed "s/ .*//") &&
+	verbose test $((1 + $before)) = $(git count-objects | sed "s/ .*//") &&
 	test_path_is_file $BLOB_FILE &&
 	test-chmtime =-$((2*$week+1)) $BLOB_FILE &&
 	git gc &&
-	test $before = $(git count-objects | sed "s/ .*//") &&
+	verbose test $before = $(git count-objects | sed "s/ .*//") &&
 	test_path_is_missing $BLOB_FILE
 
 '
@@ -144,7 +144,7 @@ test_expect_success 'gc --no-prune' '
 	test-chmtime =-$((5001*$day)) $BLOB_FILE &&
 	git config gc.pruneExpire 2.days.ago &&
 	git gc --no-prune &&
-	test 1 = $(git count-objects | sed "s/ .*//") &&
+	verbose test 1 = $(git count-objects | sed "s/ .*//") &&
 	test_path_is_file $BLOB_FILE
 
 '
@@ -209,10 +209,10 @@ test_expect_success 'gc: prune old objects after local clone' '
 	git clone --no-hardlinks . aclone &&
 	(
 		cd aclone &&
-		test 1 = $(git count-objects | sed "s/ .*//") &&
+		verbose test 1 = $(git count-objects | sed "s/ .*//") &&
 		test_path_is_file $BLOB_FILE &&
 		git gc --prune &&
-		test 0 = $(git count-objects | sed "s/ .*//") &&
+		verbose test 0 = $(git count-objects | sed "s/ .*//") &&
 		test_path_is_missing $BLOB_FILE
 	)
 '

t/test-lib-functions.sh

@@ -634,6 +634,15 @@ test_cmp_bin() {
 	cmp "$@"
 }
 
+# Call any command "$@" but be more verbose about its
+# failure. This is handy for commands like "test" which do
+# not output anything when they fail.
+verbose () {
+	"$@" && return 0
+	echo >&2 "command failed: $(git rev-parse --sq-quote "$@")"
+	return 1
+}
+
 # Check if the file expected to be empty is indeed empty, and barfs
 # otherwise.