diff-no-index: exit(1) if 'diff --quiet <repo file> <external file>' finds changes

When running 'git diff --quiet <file1> <file2>', if file1 or file2
is outside the repository, it will exit(0) even if the files differ.
It should exit(1) when they differ.

This happens because 'diff_no_index' looks at the 'found_changes'
member from 'diff_options' to determine if changes were made.  This
is the wrong thing to do, since it is only set if xdiff is actually
run and it finds a change (the diff machinery will optimize out the
xdiff call when it is not necessary) and in that case HAS_CHANGED
flag needs to be taken into account.

Use diff_result_code() that knows all these details for the correct
exit value instead.

Signed-off-by: Tim Henigan <tim.henigan@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff-no-index.c

@@ -256,5 +256,5 @@ void diff_no_index(struct rev_info *revs,
 	 * The return code for --no-index imitates diff(1):
 	 * 0 = no changes, 1 = changes, else error
 	 */
-	exit(revs->diffopt.found_changes);
+	exit(diff_result_code(&revs->diffopt, 0));
 }

t/t4035-diff-quiet.sh

@@ -10,7 +10,22 @@ test_expect_success 'setup' '
 	git commit -m first &&
 	echo 2 >b &&
 	git add . &&
-	git commit -a -m second
+	git commit -a -m second &&
+	mkdir -p test-outside/repo && (
+		cd test-outside/repo &&
+		git init &&
+		echo "1 1" >a &&
+		git add . &&
+		git commit -m 1
+	) &&
+	mkdir -p test-outside/non/git && (
+		cd test-outside/non/git &&
+		echo "1 1" >a &&
+		echo "1 1" >matching-file &&
+		echo "1 1 " >trailing-space &&
+		echo "1   1" >extra-space &&
+		echo "2" >never-match
+	)
 '
 
 test_expect_success 'git diff-tree HEAD^ HEAD' '
@@ -77,4 +92,60 @@ test_expect_success 'git diff-index --cached HEAD' '
 	}
 '
 
+test_expect_success 'git diff, one file outside repo' '
+	(
+		cd test-outside/repo &&
+		test_expect_code 0 git diff --quiet a ../non/git/matching-file &&
+		test_expect_code 1 git diff --quiet a ../non/git/extra-space
+	)
+'
+
+test_expect_success 'git diff, both files outside repo' '
+	(
+		GIT_CEILING_DIRECTORIES="$TRASH_DIRECTORY/test-outside" &&
+		export GIT_CEILING_DIRECTORIES &&
+		cd test-outside/non/git &&
+		test_expect_code 0 git diff --quiet a matching-file &&
+		test_expect_code 1 git diff --quiet a extra-space
+	)
+'
+
+test_expect_success 'git diff --ignore-space-at-eol, one file outside repo' '
+	(
+		cd test-outside/repo &&
+		test_expect_code 0 git diff --quiet --ignore-space-at-eol a ../non/git/trailing-space &&
+		test_expect_code 1 git diff --quiet --ignore-space-at-eol a ../non/git/extra-space
+	)
+'
+
+test_expect_success 'git diff --ignore-space-at-eol, both files outside repo' '
+	(
+		GIT_CEILING_DIRECTORIES="$TRASH_DIRECTORY/test-outside" &&
+		export GIT_CEILING_DIRECTORIES &&
+		cd test-outside/non/git &&
+		test_expect_code 0 git diff --quiet --ignore-space-at-eol a trailing-space &&
+		test_expect_code 1 git diff --quiet --ignore-space-at-eol a extra-space
+	)
+'
+
+test_expect_success 'git diff --ignore-all-space, one file outside repo' '
+	(
+		cd test-outside/repo &&
+		test_expect_code 0 git diff --quiet --ignore-all-space a ../non/git/trailing-space &&
+		test_expect_code 0 git diff --quiet --ignore-all-space a ../non/git/extra-space &&
+		test_expect_code 1 git diff --quiet --ignore-all-space a ../non/git/never-match
+	)
+'
+
+test_expect_success 'git diff --ignore-all-space, both files outside repo' '
+	(
+		GIT_CEILING_DIRECTORIES="$TRASH_DIRECTORY/test-outside" &&
+		export GIT_CEILING_DIRECTORIES &&
+		cd test-outside/non/git &&
+		test_expect_code 0 git diff --quiet --ignore-all-space a trailing-space &&
+		test_expect_code 0 git diff --quiet --ignore-all-space a extra-space &&
+		test_expect_code 1 git diff --quiet --ignore-all-space a never-match
+	)
+'
+
 test_done