merge-one-file: fix broken merges with alternate work trees

diff --git a/t/t4002-diff-basic.sh b/t/t4002-diff-basic.sh
index cc3681f16118ca70ae9f65a27ccd6f354a6deee1..18695ce8218a7b383258eeb0bad84b4d4bde45be 100755 (executable)
--- a/t/t4002-diff-basic.sh
+++ b/t/t4002-diff-basic.sh
@@ -258,4 +258,12 @@ test_expect_success \
     git diff-tree -r -R $tree_A $tree_B >.test-b &&
     cmp -s .test-a .test-b'
 
+test_expect_success \
+    'diff can read from stdin' \
+    'test_must_fail git diff --no-index -- MN - < NN |
+        grep -v "^index" | sed "s#/-#/NN#" >.test-a &&
+    test_must_fail git diff --no-index -- MN NN |
+        grep -v "^index" >.test-b &&
+    test_cmp .test-a .test-b'
+
 test_done