commit: don't be fooled by ita entries when creating initial commit

ita entries are dropped at tree generation phase. If the entire index
consists of just ita entries, the result would be a a commit with no
entries, which should be caught unless --allow-empty is specified. The
test "!!active_nr" is not sufficient to catch this.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/commit.c

@@ -894,9 +894,14 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
 		if (amend)
 			parent = "HEAD^1";
 
-		if (get_sha1(parent, sha1))
-			commitable = !!active_nr;
-		else {
+		if (get_sha1(parent, sha1)) {
+			int i, ita_nr = 0;
+
+			for (i = 0; i < active_nr; i++)
+				if (ce_intent_to_add(active_cache[i]))
+					ita_nr++;
+			commitable = active_nr - ita_nr > 0;
+		} else {
 			/*
 			 * Unless the user did explicitly request a submodule
 			 * ignore mode by passing a command line option we do

t/t2203-add-intent.sh

@@ -129,6 +129,16 @@ test_expect_success 'cache-tree does skip dir that becomes empty' '
 	)
 '
 
+test_expect_success 'commit: ita entries ignored in empty intial commit check' '
+	git init empty-intial-commit &&
+	(
+		cd empty-intial-commit &&
+		: >one &&
+		git add -N one &&
+		test_must_fail git commit -m nothing-new-here
+	)
+'
+
 test_expect_success 'commit: ita entries ignored in empty commit check' '
 	git init empty-subsequent-commit &&
 	(