Merge branch 'cm/diff-check-at-eol' into maint

* cm/diff-check-at-eol:
  diff --check: correct line numbers of new blank lines at EOF

Author: gitster

diff.c

@@ -2158,7 +2158,7 @@ static void builtin_checkdiff(const char *name_a, const char *name_b,
 
 			ecbdata.ws_rule = data.ws_rule;
 			check_blank_at_eof(&mf1, &mf2, &ecbdata);
-			blank_at_eof = ecbdata.blank_at_eof_in_preimage;
+			blank_at_eof = ecbdata.blank_at_eof_in_postimage;
 
 			if (blank_at_eof) {
 				static char *err;

t/t4019-diff-wserror.sh

@@ -178,6 +178,15 @@ test_expect_success 'trailing empty lines (2)' '
 
 '
 
+test_expect_success 'checkdiff shows correct line number for trailing blank lines' '
+
+	printf "a\nb\n" > G &&
+	git add G &&
+	printf "x\nx\nx\na\nb\nc\n\n" > G &&
+	[ "$(git diff --check -- G)" = "G:7: new blank line at EOF." ]
+
+'
+
 test_expect_success 'do not color trailing cr in context' '
 	git config --unset core.whitespace
 	rm -f .gitattributes &&