Merge branch 'en/tree-walk-optim'

* en/tree-walk-optim:
  diff_tree(): Skip skip_uninteresting() when all remaining paths interesting
  tree_entry_interesting(): Make return value more specific
  tree-walk: Correct bitrotted comment about tree_entry()
  Document pre-condition for tree_entry_interesting

tree-diff.c

@@ -85,6 +85,8 @@ static int compare_tree_entry(struct tree_desc *t1, struct tree_desc *t2, const
 /*
  * Is a tree entry interesting given the pathspec we have?
  *
+ * Pre-condition: baselen == 0 || base[baselen-1] == '/'
+ *
  * Return:
  *  - 2 for "yes, and all subsequent entries will be"
  *  - 1 for yes
@@ -101,7 +103,7 @@ static int tree_entry_interesting(struct tree_desc *desc, const char *base, int
 	int never_interesting = -1;
 
 	if (!opt->nr_paths)
-		return 1;
+		return 2;
 
 	sha1 = tree_entry_extract(desc, &path, &mode);
 
@@ -257,19 +259,12 @@ static void show_entry(struct diff_options *opt, const char *prefix, struct tree
 	}
 }
 
-static void skip_uninteresting(struct tree_desc *t, const char *base, int baselen, struct diff_options *opt)
+static void skip_uninteresting(struct tree_desc *t, const char *base, int baselen, struct diff_options *opt, int *all_interesting)
 {
-	int all_interesting = 0;
 	while (t->size) {
-		int show;
-
-		if (all_interesting)
-			show = 1;
-		else {
-			show = tree_entry_interesting(t, base, baselen, opt);
-			if (show == 2)
-				all_interesting = 1;
-		}
+		int show = tree_entry_interesting(t, base, baselen, opt);
+		if (show == 2)
+			*all_interesting = 1;
 		if (!show) {
 			update_tree_entry(t);
 			continue;
@@ -284,14 +279,20 @@ static void skip_uninteresting(struct tree_desc *t, const char *base, int basele
 int diff_tree(struct tree_desc *t1, struct tree_desc *t2, const char *base, struct diff_options *opt)
 {
 	int baselen = strlen(base);
+	int all_t1_interesting = 0;
+	int all_t2_interesting = 0;
 
 	for (;;) {
 		if (DIFF_OPT_TST(opt, QUICK) &&
 		    DIFF_OPT_TST(opt, HAS_CHANGES))
 			break;
 		if (opt->nr_paths) {
-			skip_uninteresting(t1, base, baselen, opt);
-			skip_uninteresting(t2, base, baselen, opt);
+			if (!all_t1_interesting)
+				skip_uninteresting(t1, base, baselen, opt,
+						   &all_t1_interesting);
+			if (!all_t2_interesting)
+				skip_uninteresting(t2, base, baselen, opt,
+						   &all_t2_interesting);
 		}
 		if (!t1->size) {
 			if (!t2->size)