Merge branch 'jk/diff-not-so-quick'

* jk/diff-not-so-quick:
  diff: futureproof "stop feeding the backend early" logic
  diff_tree: disable QUICK optimization with diff filter

Conflicts:
	diff.c

diff-lib.c

@@ -102,9 +102,7 @@ int run_diff_files(struct rev_info *revs, unsigned int option)
 		int changed;
 		unsigned dirty_submodule = 0;
 
-		if (DIFF_OPT_TST(&revs->diffopt, QUICK) &&
-		    !revs->diffopt.filter &&
-		    DIFF_OPT_TST(&revs->diffopt, HAS_CHANGES))
+		if (diff_can_quit_early(&revs->diffopt))
 			break;
 
 		if (!ce_path_match(ce, &revs->prune_data))

diff.c

@@ -4456,6 +4456,13 @@ int diff_result_code(struct diff_options *opt, int status)
 	return result;
 }
 
+int diff_can_quit_early(struct diff_options *opt)
+{
+	return (DIFF_OPT_TST(opt, QUICK) &&
+		!opt->filter &&
+		DIFF_OPT_TST(opt, HAS_CHANGES));
+}
+
 /*
  * Shall changes to this submodule be ignored?
  *

diff.h

@@ -198,6 +198,8 @@ extern void diff_tree_combined_merge(const unsigned char *sha1, int, struct rev_
 
 void diff_set_mnemonic_prefix(struct diff_options *options, const char *a, const char *b);
 
+extern int diff_can_quit_early(struct diff_options *);
+
 extern void diff_addremove(struct diff_options *,
 			   int addremove,
 			   unsigned mode,

t/t4040-whitespace-status.sh

@@ -67,4 +67,9 @@ test_expect_success 'diff-files --diff-filter --quiet' '
 	test_must_fail git diff-files --diff-filter=M --quiet
 '
 
+test_expect_success 'diff-tree --diff-filter --quiet' '
+	git commit -a -m "worktree state" &&
+	test_must_fail git diff-tree --diff-filter=M --quiet HEAD^ HEAD
+'
+
 test_done

tree-diff.c

@@ -142,8 +142,7 @@ int diff_tree(struct tree_desc *t1, struct tree_desc *t2,
 	strbuf_add(&base, base_str, baselen);
 
 	for (;;) {
-		if (DIFF_OPT_TST(opt, QUICK) &&
-		    DIFF_OPT_TST(opt, HAS_CHANGES))
+		if (diff_can_quit_early(opt))
 			break;
 		if (opt->pathspec.nr) {
 			skip_uninteresting(t1, &base, opt, &t1_match);