Fix 'git diff --no-index' with a non-existing symlink target

When trying to find out mode changes, we should not access the symlink
targets using stat(); instead we use lstat() so that the diff does
not fail trying to find a non-existing symlink target.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff-no-index.c

@@ -40,7 +40,7 @@ static int get_mode(const char *path, int *mode)
 		*mode = 0;
 	else if (!strcmp(path, "-"))
 		*mode = create_ce_mode(0666);
-	else if (stat(path, &st))
+	else if (lstat(path, &st))
 		return error("Could not access '%s'", path);
 	else
 		*mode = st.st_mode;

t/t4011-diff-symlink.sh

@@ -82,4 +82,11 @@ test_expect_success \
     git diff-index -M -p $tree > current &&
     compare_diff_patch current expected'
 
+test_expect_success \
+    'diff symlinks with non-existing targets' \
+    'ln -s narf pinky &&
+    ln -s take\ over brain &&
+    test_must_fail git diff --no-index pinky brain > output 2> output.err &&
+    grep narf output &&
+    ! grep error output.err'
 test_done